Lubricant Composition

ABSTRACT

The present invention provide a lubricant composition comprising a lubricant base oil, wherein said lubricant composition contains 0.08% by mass or less of zinc dithiophosphate or no zinc dithiophosphate as phosphorus amount for total amount of said lubricant composition, contacts metallic materials containing lead, and contains at least a kind of additive selected from a group consisting of following (A)˜(D): (A) organomolybdenum compounds (except molybdenum dithiophosphate); (B) borate ester and/or derivatives thereof; (C) organomolybdenum compounds, and borate ester and/or derivatives thereof; and (D) organomolybdenum compounds, and borated alkyl or alkenyl succinimide.

TECHNICAL FIELD

The present invention relates to a lubricant composition that enables to inhibit corrosion or corrosive wear of metallic materials containing lead, metallic materials containing copper-lead, or both of the metallic materials containing lead and metallic materials containing copper. In particular, the present invention relates to a lubricant composition that enables to inhibit corrosion or corrosive wear of the above materials even if the content of zinc dithiophosphate is small.

BACKGROUND ART

Slide materials for engine and so on mainly consist of ferrous-series and aluminum-series metallic materials. Among the slide materials, however, for making slide members of main bearing and connecting rod bearing such as bearing metal, not only metallic materials like aluminum, copper, and tin, but also metallic material containing lead and metallic material containing copper-lead are sometimes used. Such metallic materials containing lead have an excellent feature that it has little fatigue phenomena, whereas the material has a fault that the corrosive wear thereof is easily caused.

Causes of corrosive wear include accumulation of peroxide originated from the oil deterioration (e.g., Non-Patent Document 1) and direct oxidization by oxygen molecules in the air (e.g., Non-Patent Documents 2˜4). In addition, oxidation product like quinine, diacetyl, nitrogen oxides, and nitro compounds are known that those products promote the corrosion under a condition of coexistence with acid (e.g., Non-Patent Document 5). The reality of cause of corrosion is more complex, as it is controlled by many factors. However, in order to inhibit corrosion, generally:

prevention of oxidation of lubricant;

destruction of oxidized substance;

inhibition of production of corrosive oxidation product;

inactivation of oxidized substance; and

formation of anticorrosive coating on the metal surface,

are important. More precisely, anticorrosive effect obtained by addition of:

peroxide decomposer-cum-anticorrosive coating former such as zinc dithiophosphate and sulfide;

chain-termination type antioxidant such as amine series and phenol series;

anticorrosive coating former like benzotriazole; and

acid neutralizing agent like

detergent-and-dispersant,

are known. In general, most of these components are used at the same time.

Particularly, for inhibiting corrosive wear of slide materials containing lead, anti-wear agent containing sulfur such as zinc dithiophosphate is distinctively effective. For example, in Patent Document 2, an engine oil composition, to which zinc dialkyl dithiophosphoric acid is added with other components and which is excellent in anticorrosive property for bearing metal, is disclosed.

In the conventional engine oil mixed with zinc dithiophosphate as approximately 0.1% by mass or more of phosphorus (approximately0.2% by mass of sulfur, with peroxide decomposing effect and inactivation of lead surface, excellent lead corrosive-wear inhibiting effect is realized. Nevertheless, it is known that when the content of zinc dithiophosphate is reduced, the corrosive-wear inhibiting effect of lead is exponentially deteriorated (e.g., Non-Patent Document 6).

With the increasing requirement of reduction of environmental burdens these days, requirement to have products of low phosphorus content or low-sulfur content is increasing as well as the requirement of further extension of engine oil life to become even further longer. The further extension of engine oil life, from the view point of base number preservation, is achieved by reduction of sulfur content of the fuel for gasoline engine and diesel engine, inhibition of engine-oil deterioration caused by the fuel such as the spread of gas-fueled engine, and higher-performance of engine oil itself (with optimal mixture of antioxidant, anti-wear agent, metal series cleaner, and other additives) (e.g., Patent Document 1).

Non-Patent Document 1: Ind. Eng. Chem., 36 (1944), 477

Non-Patent Document 2: Ind. Eng. Chem., 37 (1945), 90

Non-Patent Document 3: Ind. Eng. Chem., 49 (1957), 1703

Non-Patent Document 4: J. Inst. Petrol., 37 (1951), 225

Non-Patent Document 5: Ind. Eng. Chem., 37 (1945), 917

Non-Patent Document 6: SAKURAI, Toshio (editor), “Sekiyu-seihin Tenkazai (Additives for Petroleum Product)” 2nd Edition, p. 271, FIG. 8 (issued by Saiwai-Shoho, Jun. 15, 1979)

Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2002-294271

Patent Document 2: JP-A No. 07-268379

DISCLOSURE OF THE INVENTION Problems to be solved by the Invention

As mentioned above, the conventional engine oil in which zinc dithiophosphate is mixed can realize an excellent lead corrosive-wear inhibiting effect for lead series materials. However, for the slide members containing nonferrous base metals other than lead (e.g., copper, tin, silver, and etc.), there is a problem that the engine oil tends to cause sulfur corrosive wear. Instead of using zinc dithiophosphate, anticorrosive coating former like benzotriazole can be considered as an alternative. This anticorrosive coating former is effective for inhibiting corrosion of copper, whereas it does not work sufficiently for inhibiting corrosion of lead. Thereby, in order to inhibit the corrosion of parts in which metallic materials containing copper and lead are used, a corrosion inhibitor, which is excellent in anticorrosive property for both copper and lead, is need to be developed.

Accordingly, a first object of the present invention is to provide a corrosion inhibitor which is effective for inhibiting corrosion and corrosive wear of metallic material containing lead but also metallic material containing lead-copper or both of metallic material containing copper and metallic material containing lead, and to provide a lubricant composition obtained by adding the corrosion inhibitor.

Further, from the view point of reduction of environmental burdens, with the engine oil in which the content of zinc dithiophosphate is reduced or which does not contain zinc dithiophosphate but contain small amount of phosphorus, and/or which content of sulfur is reduced, the inventor of the invention examined the wear prohibiting performance for individual slide members (ferrous series, aluminum series, copper series, lead series, and etc.) in case of use for even longer period of time than ever before. As a result, although the lubricant's total base number remains sufficiently and the lubricant does not reach the end of the product life, it is found out that corrosive wear of the slide materials containing lead can be significantly caused. Especially, the lead corrosion is remarkable under an oxidized gas atmosphere. Thus, it is assumed that, by having reduction and nonuse of zinc dithiophosphate or by loosing the same due to the long-term use, peroxide decomposing effect and corrosive-wear inhibiting effect of lead declines or disappears. While deterioration products of the lubricant affect the lead surface, which accelerate the lead corrosion. This lead corrosion phenomenon is caused despite the existence of sufficient detergent and of acid-neutralizing performance as well as antioxidant performance. Therefore, inhibiting this lead corrosion phenomenon is exposed as a new problem caused by the reduction or nonuse of zinc dithiophosphate that conventionally generally used in the lubricant composition.

In other words, a second object of the present invention is to provide a lubricant composition which enables to inhibit lead corrosion caused under a condition with remaining base number after a long-term use, even where corrosion of a slide material containing lead is significant because of the reduction or nonuse of zinc dithophosphate.

Means for Solving the Problems

The inventor of the present invention has conducted serious studies in order to solve the problem. As a result, the present inventor has acquired an idea that in case of little or no content of zinc dithiophosphate, by adding a combination of particular compounds to the lubricant, the corrosion or corrosive wear of metallic material containing lead can be effectively inhibited, thereby the invention is completed.

The first invention is a lubricant composition comprising a lubricant base oil, wherein the lubricant composition contains 0.08% by mass or less of zinc dithiophosphate or no zinc dithiophosphate as phosphorus amount for total amount of the lubricant composition, contacts metallic materials containing lead, and contains at least a kind of additive selected from a group consisting of following (A)˜(D):

(A) organomolybdenum compounds (except molybdenum dithiophpsphate;

(B) borate ester and/or derivatives thereof;

(C) organomolybdenum compounds, and borate ester and/or derivatives thereof; and

(D) organomolybdenum compounds, and borated alkyl or alkenyl succinimide.

The wording “borated alkyl or alkenyl succinimide” means “borated alkyl succinimide” or “borated alkenyl succinimide” (hereinafter, same as the above meaning in the present specification.).

In the first invention, the organomolybdenum compounds are preferably compounds obtained by reaction of any one kind of compound selected from a group consisting of: sulfur-free organic acid, amine, amide, imide, and compounds having alcoholic hydroxyl group, with tetra- to hexa-valent molybdenum compounds.

In the above first invention, the organomolybdenum compounds are at least any one kind of compound selected from a group consisting of following (a)˜(e):

(a) a salt of at least a kind of acid containing phosphorus selected from a group consisting of: phosphate monoester, phosphate monoester, phosphate diester, phosphate diester, phosphonous acid, phosphonic acid, phosphonous acid monoester, and phosphonic acid monoester, respectively having at least an alkyl group of carbon number 3 to 30, with molybdenum compounds;

(b) a complex of a kind of amine compound selected from a group consisting of: primary amine, secondary amine, and alkanolamine, respectively having at least an alkyl group or an alkenyl group of carbon number 3 to 30, with molybdenum compounds;

(c) a salt or an ester of alcohols having at least an alcoholic hydroxyl group selected from a group consisting of: monovalent alcoholes, polyvalent alcohols, and partial ester or partial ether of the polyvalent alcohols of carbon number 3 to 30, with molybdenum compounds;

(d) a salt or an ester of amide compounds having at least an alkyl group or an alkenyl group of carbon number 3 to 30 and alcoholic hydroxyl groups, with molybdenum compounds; and

(e) a salt of fatty acids of carbon number 3 to 30 with molybdenum compounds.

The lubricant composition of the above first invention preferably further comprising one or more kind of additives selected from a group consisting of: antioxidant, anti-wear agent other than zinc dithiophosphate, and metallic detergent.

The lubricant composition of the above first invention is suitably used for internal combustion engine of which slide members contain a metallic materials containing lead.

The lubricant composition of the above first invention can be used for a lubricant composition which contacts metallic materials containing lead, metallic materials containing copper-lead, or both of the metallic materials containing lead and the metallic materials containing copper; in such a case, the organomolybdenum compounds are preferably compounds obtained by reaction of any one kind of compound selected from a group consisting of: sulfur-free organic acid except carboxylic acid, amine, amide, imide, and compounds having alcoholic hydroxyl groups, with tetra- to hexa-valent molybdenum compounds.

The second invention is a method for inhibiting corrosion or corrosive wear of a metallic materials containing lead having a contact with a lubricant composition comprising a lubricant base oil, wherein the lubricant composition contains 0.08% by mass or less of zinc dithiophosphate or no zinc dithiophosphate as phosphorus amount for total amount of the lubricant composition, and the lubricant composition contains at least a kind of additive selected from a group consisting of following (A)˜(D):

(A) organomolybdenum compounds (except molybdenum dithiophosphoric acid);

(B) borate ester and/or derivatives thereof;

(C) organomolybdenum compounds, and borate ester and/or derivatives thereof; and

(D) organomolybdenum compounds, and borated alkyl or alkenyl succinimide.

According to the method of the second invention,

the method can inhibit corrosion or corrosive wear of metallic materials containing lead, metallic materials containing copper-lead, or both of the metallic materials containing lead and the metallic materials containing copper. In such a case, organomolybdenum compounds among said additives are preferably compounds obtained by reaction of any one kind of compound selected from a group consisting of: sulfur-free organic acid except carboxylic acid, amine, amide, imide, and compounds having alcoholic hydroxyl groups, with tetra- to hexa-valent molybdenum compounds.

The third invention is an anticorrosion or anticorrosive-wear agent for copper and lead, wherein the agent is an additive added to a lubricant composition comprising a lubricant base oil, contains 0.08% by mass or less of zinc dithiophosphate or no zinc dithiophosphate as phosphorus amount for total amount of the lubricant composition, contacts metallic materials containing lead, metallic materials containing copper-lead, or both of the metallic materials containing lead and the metallic materials containing copper, and further contains organomolybdenum compounds obtained by reaction of any one kind of compound selected from a group consisting of: sulfur-free organic acid except carboxylic acid, amine, amide, imide, and compounds having alcoholic hydroxyl group, with tetra- to hexa-valent molybdenum compounds.

The fourth invention is a use of a lubricant composition for lubricating metallic materials containing lead in an apparatus having metallic materials containing lead therein, wherein the lubricant composition comprises a lubricant base oil, contains 0.08% by mass or less of zinc dithiophosphate or no zinc dithiophosphate as phosphorus amount for total amount of the lubricant composition, and contains at least a kind of additive selected from a group consisting of following (A)˜(D):

-   (A) organomolybdenum compounds (except molybdenum dithiophosphoric     acid); -   (B) borate ester and/or derivatives thereof; -   (C) organomolybdenum compounds, and borate ester and/or derivatives     thereof; and -   (D) organomolybdenum compounds, and borated alkyl or alkenyl     succinimide.

EFFECTS OF THE INVENTION

The lubricant composition of the present invention, particularly in the case of reduction or nonuse of zinc dithiophosphate which is significantly effective for inhibiting lead corrosion or corrosive wear, can inhibit lead corrosion or corrosive wear and suitably used under a contact with metallic materials containing lead. This lubricant composition is low-sulfur, further, low-phosphorus and low-ash, and is excellent in long drain performance.

Further, the lubricant composition of the invention that limits the organomolybdenum compounds to a particular compound is excellent in anticorrosive property for both lead and copper. Accordingly, the lubricant composition obtained by adding the above particular compound can effectively inhibit corrosion or corrosive wear of metallic materials containing copper-lead or both of the metallic materials containing copper and metallic materials containing lead, at the same time.

Thus, the lubricant composition of the invention can be suitably used as a lubricant for internal combustion engine contacting metallic materials containing lead (in the aspect thereof limiting the organomolybdenum compound to a particular one, the lubricant for internal combustion engine contacting metallic materials containing lead, metallic materials containing copper, metallic materials containing lead-copper: hereinafter, these can be described as “metallic materials containing lead and the like”.), especially diesel engine oil and gas engine oil having lead-series slide materials. But also, the lubricant composition of the invention can be suitably used as a lubricant for apparatus having a lubrication system where the lubricant contacts the metallic materials containing lead and the like. The examples include: a lubricant for drive-train such as automatic transmission, manual transmission, continuously variable transmission, and gears; lubricant such as wet-type brake oil, hydraulic oil, turbine oil, compressor oil, bearing oil, and refrigerant oil.

BEST MODE FOR CARRYING OUT THE INVENTION

The lubricant composition of the invention having contact with metallic materials containing lead contains 0.08% by mass or less of zinc dithiophosphate or no zinc dithiophosphate as phosphorus amount for total amount of the lubricant composition, and enables to inhibit corrosion or corrosive wear being pronounced under the above circumstance. The constitution of the invention is that a lubricant composition comprises a lubricant base oil, wherein the lubricant composition contains 0.08% by mass or less of zinc dithiophosphate or no zinc dithiophosphate as phosphorus amount for total amount of the lubricant composition, contacts metallic materials containing lead, and contains at least a kind of additive selected from a group consisting of following (A)˜(D):

(A) organomolybdenum compounds (except molybdenum dithiophosphate);

(B) borate ester and/or derivatives thereof;

(C) organomolybdenum compounds, and borate ester and/or derivatives thereof; and

(D) organomolybdenum compounds, and borated alkyl or alkenyl succinimide.

An embodiment of lubricant composition of the present invention that limits the organomolybdenum compounds to a particular compound can be used as a lubricant composition having contact with metallic materials containing lead, metallic materials containing copper-lead, or both of metallic materials containing lead and metallic materials containing copper.

Firstly, metallic materials to be lubricated by the lubricant composition of the invention will be described as follows.

<Metallic Materials Containing Lead>

In the invention, the metallic materials containing lead is not limited as long as lead exists on the metallic surface where the lubricant of the invention contacts. Examples of the metallic materials containing lead include not only lead, but also lead alloy, or metallic materials whose respective metal-base surface is covered with lead or lead alloy. Also, the metallic materials containing lead include a type of material whose surface is covered with metallic material containing non-lead metal. However, over the period of use, the covering surface wears away and the metallic material containing lead hidden underneath is exposed, then it is possible for the metallic materials containing lead to contact the lubricant of the invention. Examples of lead alloy include: lead-tin alloy, lead-copper alloy, lead-tin-copper alloy, lead-aluminum alloy, lead-aluminum-silicon alloy, lead-aluminum-tin alloy, lead-aluminum-copper alloy, lead-aluminum-silicon-tin alloy, lead-aluminum-silicon-copper alloy, lead-aluminum-tin-copper alloy, lead-aluminum-silicon-tin-copper alloy, and the like. The above metallic materials containing lead are such that the lead content is preferably 1% by mass or more, more preferably 2% by mass or more, further preferably 5% by mass or more, furthermore preferably 10% by mass or more. More precisely, a lead-tin alloy containing 50˜95% by mass of lead, more preferably 60˜90% by mass of lead; a lead-copper alloy containing 5˜50% by mass of lead, more preferably 10˜30% by mass of lead; and a lead-aluminum alloy containing 1˜10% by mass of lead, more preferably 2˜5% by mass of lead can be the examples. If the lead content on the metal surface is higher, lead corrosion or corrosive wear can be easily caused, therefore the lubricant composition of the invention is useful.

<Metallic Materials Containing Copper-Lead>

In the invention, metallic materials containing copper-lead are not limited as long as copper and lead exist on the metal surface having contact with the lubricant of the invention. The examples include copper-lead alloy or metallic materials whose respective metal-base surface is covered with copper-lead alloy. Moreover, the metallic materials containing copper-lead include a type of material whose surface is covered with metallic material containing non-copper-lead metal, however, over the period of use, the covering surface wears away and the metallic material containing copper-lead hidden underneath is exposed, then it is possible for the metallic materials containing lead to contact the lubricant of the invention.

As copper-lead alloys, the examples include copper-lead alloy, lead-tin-copper alloy, lead-aluminum-copper alloy, lead-aluminum-silicon-copper alloy, lead-aluminum-tin-copper alloy, and lead-aluminum-silicon-tin-copper alloy. More precisely, a metallic material containing copper-lead whose lead content is 5˜50% by mass, preferably 10˜30% by mass can be an example.

Apart from the abovementioned metallic materials containing lead and metallic materials containing copper-lead, the embodiment of lubricant composition of the present invention that limits the organomolybdenum compounds can be used as a lubricant having contact with each of metallic materials containing copper and metallic materials containing lead.

The components constituting the lubricant composition of the invention include a lubricant base oil, zinc dithiophosphate, and the abovementioned additives (A)˜(D). The individual components of the lubricant composition will be described as follows.

<Lubricant Base Oil>

The lubricant base oil in the invention is not particularly limited; mineral base oil and synthetic base oil for normal lubricant can be used. Examples of the mineral base oil include base oils produced by a method of refining lubricant fraction, which obtained by vacuum distillation of reduced crude obtained by atmospheric distillation of crude oil, with one or more treatment selected from a group consisting of solvent deasphalting, solvent extraction, hydrocracking, dewaxing, hydrorefining. Another example of the mineral base oil is produced by a method of isomerizing slack wax or GTL WAX (gas to liquid wax).

Sulfur content in the mineral base oil is not limited; sulfur is normally included 0˜1.5% by mass, preferably 0.2% by mass or less, more preferably 0.05% by mass or less, furthermore preferably 0.005% by mass or less. As a lubricant having excellent long-drain performance and used for internal combustion engine, it is possible to obtain a low-sulfur lubricant composition which is capable to prevent adverse influence to exhaust-gas aftertreatment apparatus as much as possible.

While, saturated fraction of the mineral base oil is not particularly limited; the saturated fraction is normally 50˜100% by mass. From the view point of excellent oxidation stability and long-drain performance, it is preferably 60% by mass or more, more preferably 90% by mass or more, furthermore preferably 95% by mass or more. The wording of the above “saturated fraction” means a saturated fraction measured in accordance with ASTM D2549.

Examples of synthetic base oil particularly include: polybutene or hydride thereof; poly-α-olefin or hydride thereof such as 1-octeneoligomer, 1-deceneoligomer; diester such as ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, and di-2-ethylhexyl sabacate; polyol ester such as neopentyl glycol ester, trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerylthritol-2-ethylhexanoate and pentaerylthritol pelargonate; aromatic synthetic oil such as alkyl naphthalene, alkyl benzene; or mixture thereof; and the like.

As the lubricant base oil in the invention, the above mineral base oil, synthetic base oil, or two or more kinds of optional mixture selected from these two types of base oil, and so on, can be used. Examples include more than one kind of mineral base oil, more than one kind of synthetic base oil, mixture of more than one kind of mineral base oil and more than one kind of synthetic base oil.

Kinematic viscosity of the lubricant base oil in the invention is not particularly limited; the kinematic viscosity at 100° C. is preferably 20 mm²/s or less, more preferably 16 mm²/s or less. While, it is preferably 3 mm²/s or more, more preferably 5 mm²/s or more. When the kinematic viscosity at 100° C. is more than 20 mm²/s, low-temperature viscosity property is deteriorated. On the other hand, when the kinematic viscosity at 100° C. is less than 3 mm²/s, the lubricity of oil falls due to the insufficient oil-film forming at the area to be lubricated, and evaporative loss of the lubricant base oil increases. Therefore, both cases are not preferable.

As the amount of evaporative loss of the lubricant base oil, NOACK evaporation is preferably 20% by mass or less, more preferably 16% by mass or less, furthermore preferably 10% by mass or less, even more preferably 6% by mass or less, and 5% by mass or less is particularly preferable. When NOACK evaporation of the lubricant base oil is over 20% by mass, evaporative loss of the lubricant is high and results in inferior long drain performance. But also, if it is used as lubricant for internal combustion engine, sulfur compound, phosphorus compound, and metallic portion in the composition might be accumulated within the exhaust-gas treating apparatus together with the lubricant base oil, an adverse influence to the exhaust-gas treating apparatus is feared. The wording of the above “NOACK evaporation” means an evaporation measured in accordance with ASTM D5800.

Viscosity index of the lubricant base oil is not particularly limited; so as to obtain excellent viscosity characteristics from low temperature to high temperature, the viscosity index is preferably 80 or more, more preferably 100 or more, further more preferably 120 or more. Upper limit of the viscosity index is not particularly limited; base oil having the index value of 135˜180 such as isoparaffinic mineral oil obtained by isomeraizing normal paraffin, slack wax and GTL wax can be used. Base oil having the viscosity index of 150˜250 such as complex ester-series base oil and HVI-PAO-series base oil can also be used. Lubricant base oil having the viscosity index of less than 80 is not preferable due to the deterioration of low-temperature viscosity characteristics.

<Zinc Dithiophosphate>

Zinc dithiophosphate in the invention includes an example represented by the following general formula (1) .

In the formula (1), R¹, R², R³ and R⁴ are respectively indicate hydrocarbon radicals of carbon number 1 to 24; as such hydrocarbon radicals of carbon number 1 to 24, any one of the followings are preferable: straight-chain type or branching type alkyl group of carbon number 1 to 24; straight-chain type or branching type alkenyl group of carbon number 3 to 24; cycloalkyl group or straight-chain type or branching type alkyl cycloalkyl group of carbon number 5 to 13; aryl group or straight-chain type or branching type alkylaryl group of carbon number 6 to 18; and arylalkyl group of carbon number 7 to 19; and so on. The above alkyl group and alkenyl group may be in any one of forms selected from primary, secondary, and tertiary form.

Among the above hydrocarbon radicals of possible configurations with R¹, R², R³ and R⁴, it is most preferable, when the hydrocarbon radicals are: straight-chain type or branching type alkyl group of carbon number of 1 to 18, or aryl group of carbon number 6 to 18, and straight-chain type or branching type alkylaryl group of carbon number of 6 to 18.

Production method of zinc dithiophosphate can be optional conventional method and it is not limited. For example, it can be synthesized by reacting an alcohol or a phenol having hydrocarbon radicals corresponding to the above R¹, R², R³ and R⁴ with diphosphorus pentasulfide to make dithiophosphoric acid, then, by neutralizing the obtained dithiophosphoric acid with zinc oxide. The configuration of each zinc dithiophosphate is different depends on the ingredient alcohol to be used.

Upper limit of the content of zinc dithiophosporic acid in the lubricant composition of the invention is 0.08% by mass or less as phosphorus amount, preferably 0.06% by mass or less, more preferably 0.05% by mass or less, particularly preferably 0.04% by mass or less. While, the lower value is not limited; from the view point of base number preservation, it is desirable not to contain this substance in the composition. However, if necessary, it is still possible to contain this in order to improve the corrosion or corrosive-wear inhibiting performance of metallic materials containing lead. In such a case, the content is preferably 0.01% by mass or more as the phosphorus amount, 0.02% by mass is more preferable.

When the content of zinc dithiophosphate is over 0.08% by mass as the phosphorus amount, for instance, in case of 0.10% by mass or more as the phosphorus amount, the oil is conventional lubricant which is out of the condition where the problems to be solved by the present invention is most remarkable. Therefore, even though it is excellent in corrosion or corrosive-wear inhibiting performance, from the view point of low-sulfur, low-phosphorus, or further extension of product life, it is not preferable.

<Organomolybdenum Compounds>

An embodiment of the lubricant composition of the invention includes organomolybdenum compounds. From the view point of easier prohibition of corrosion or corrosive wear of metallic materials containing lead, the organomolybdenum compound is preferably a compound obtained by a reaction of a kind of compound selected from a group consisting of: sulfur-free organic acid, amine, amide, imide, and compounds having alcoholic hydroxyl groups, with tetra- to hexa-valent molybdenum compounds.

Moreover, especially, in the lubricant composition of the invention which contacts metallic materials containing lead, metallic materials containing copper-lead, or both of the metallic materials containing lead and the metallic materials containing copper, the sulfur-free organic acid which produce organomolybdenum compound is preferably an organic acid other than carboxylic acid.

Hereinafter, individual compounds which can participate into the production of the organomolybdenum compound are described.

(Sulfur-Free Organic Acid)

As sulfur-free organic acid, acid containing phosphorus represented by the following general formulas (2) and (3) can be the examples.

(In the formula (2), n indicates 1 or 0, R⁵ indicates hydrocarbon radicals of carbon number 1 to 30. R⁶ and R⁷ may be the same or different from each other, each of them indicates hydrogen atom or hydrocarbon radicals of carbon number 1 to 30, at least one of them is hydrogen atom.)

(In the formula (3), n indicates 1 or 0, R⁸ indicates hydrocarbon radicals of carbon number 1 to 30. R⁹ and R¹⁰ may be the same or different from each other, each of them indicates hydrogen atom or hydrocarbon radicals of carbon number 1 to 30, at least one of them is hydrogen atom.)

As hydrocarbon radicals of carbon number 1 to 30 represented by R⁵˜R¹⁰ in the general formulas (2) and (3), in particular, alkyl group, cycloalkyl group, alkenyl group, alkyl-substituted cycloalkyl group, aryl group, alkyl-substituted aryl group, and arylalkyl group can be the examples.

The above alkyl group are, for example, alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group (these alkyl groups may be straight-chain type or branching type.).

The above cycloalkyl group are, for example, cycloalkyl groups of carbon number 5 to 7 such as cyclopentyl group, cyclohexyl group, cycloheptyl group. Further, the above alkylcycloalkyl groups are, for example, alkyl cycloalkyl groups of carbon number 6 to 11 such as methylcyclopentyl group, dimethylcyclopentyl group, methylethylcyclopentyl group, diethylcyclopentyl group, methylcyclohexyl group, dimethylcyclohexyl group, methylethylcyclohexyl group, diethylcyclohexyl group, methylcycloheptyl group, dimethylcycloheptyl group, methylethyl cycloheptyl group, diethyl cycloheptyl group (substitution site for the cycloalkyl group of alkyl group is optional).

The above alkenyl groups are, for example, alkenyl groups such as butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group (these alkenyl groups may be straight-chain type or branching type, and also site of double bonds is optional.).

The above aryl groups are, for example, aryl groups such as phenyl group and naphthyl group. Also, as the above alkylaryl group, the examples include alkylaryl group of carbon number 7 to 18 such as tolyl group, xylyl group, ethylphenyl group, propylphenyl group, butylphenyl group, pentylphenyl group, hexylphenyl group, heptylphenyl group, octylphenyl group, nonylphenyl group, decylphenyl group, undecylphenyl group, dodecylphenyl group (the alkyl group may be straight-chain type or branching type alkyl group, and substitution site for the aryl group is optional.).

The above arylalkyl groups are, for example, arylalkyl groups of carbon number 7 to 12 such as benzyl group, phenylethyl group, phenylpropyl group, phenylbutyl group, phenylpentyl group, phenylhexyl group (the alkyl group may be straight-chain type or branching type alkyl group.).

The hydrocarbon radicals of carbon number 1 to 30 represented by the above R⁵˜R¹⁰ are preferably alkyl groups of carbon number 1 to 30 or aryl groups of carbon number 6 to 24, more preferably, alkyl groups of carbon number 3 to 18, further preferably alkyl groups of carbon number 4 to 12.

Examples of acid containing phosphorus represented by the general formula (2) include the above phosphite monoester having a hydrocarbon radical of carbon number 1 to 30, (hydrocarbyl) phosphonous acid, the above phosphite diester having two hydrocarbon radicals of carbon number 1 to 30, (hydrocarbyl) phosphonous acid monoester, and mixture thereof.

Examples of acid containing phosphorus represented by the general formula (3) include the above phosphate monoester having a hydrocarbon radical of carbon number 1 to 30, (hydrocarbyl) phosphonic acid, the above phosphate diester having two hydrocarbon radicals of carbon number 1 to 30, (hydrocarbyl) phosphonic acid monoester, and mixture thereof.

Also, examples of sulfur-free organic acid can include carboxylic acid; examples of the carboxylic acid can include both of monobasic acid and polybasic acid.

As the monobasic acid, normally fatty acids of carbonnumber 2 to 30, preferably fatty acids of carbon number 4 to 24. The fatty acids may be straight-chain type or branching type, and may be saturated or unsaturated. In particular, the examples include: saturated fatty acid such as acetic acid, propionic acid, straight-chain type or branching type butanoic acid, straight-chain type or branching type pentanoic acid, straight-chain type or branching type hexanoic acid, straight-chain type or branching type heptanoic acid, straight-chain type or branching type octanoic acid, straight-chain type or branching type nonanoic acid, straight-chain type or branching type decanoic acid, straight-chain type or branching type undecanoic acid, straight-chain type or branching type dodecanoic acid, straight-chain type or branching type tridecanoic acid, straight-chain type or branching type tetradecanoic acid, straight-chain type or branching type pentadecanoic acid, straight-chain type or branching type hexadecanoic acid, straight-chain type or branching type heptadecanoic acid, straight-chain type or branching type octadecanoic acid, straight-chain type or branching type hydroxyoctadecanoic acid, straight-chain type or branching type nonadecanoic acid, straight-chain type or branching type icosanoic acid, straight-chain type or branching type henicosanoic acid, straight-chain type or branching type docosanoic acid, straight-chain type or branching type tricosanoic acid, straight-chain type or branching type tetracosanoic acid; unsaturated fatty acid such as acrylic acid, straight-chain type or branching type butenoic acid, straight-chain type or branching type pentenoic acid, straight-chain type or branching type hexenoic acid, straight-chain type or branching type heptenoic acid, straight-chain type or branching type octenoic acid, straight-chain type or branching type nonenoic acid, straight-chain type or branching type decenoic acid, straight-chain type or branching type undecenoic acid, straight-chain type or branching type dodecenoic acid, straight-chain type or branching type tridecenoic acid, straight-chain type or branching type tetradecenoic acid, straight-chain type or branching type pentadecenoic acid, straight-chain type or branching type hexadecenoic acid, straight-chain type or branching type heptadecenoic acid, straight-chain type or branching type octadecenoic acid, straight-chain type or branching type hydroxyoctadecenoic acid, straight-chain type or branching type nonadecenoic acid, straight-chain type or branching type icosenoic acid, straight-chain type or branching type henicosenoic acid, straight-chain type or branching type docosenoic acid, straight-chain type or branching type tricosenoic acid, straight-chain type or branching type tetracosenoic acid; and mixtures thereof.

Further, as the monobasic acid, other than the above fatty acids, monocyclic-or polycyclic carboxylic acid (it may have hydroxyl group.) may be used. The carbon number thereof is preferably 1 to 30, more preferably 7 to 30. Examples of monocyclic or polycyclic carboxylic acid include such as aromatic carboxylic acid or cycloalkyl carboxylic acid having zero to three (preferably one or two) straight-chain type or branching type alkyl groups of carbon number 1 to 30, preferably that of carbon number 1 to 20. In particular, (alkyl) benzene carboxylic acid, (alkyl) naphthalene carboxylic acid, (alkyl) cycloalkyl carboxylic acid and so on can be the examples. Preferable examples of monocyclic or polycyclic carboxylic acid include benzoic acid, salicylic acid, alkyl benzoic acid, alkyl salicylic acid, and cyclohexane carboxylic acid.

Also, as the polybasic acids, the examples include dibasic acid, tribasic acid, and tetrabasic acid. The polybasic acids may be aliphatic polybasic acid or cyclic polybasic acid. Moreover, the aliphatic polybasic acid may be straight-chain type or branching type, and it also may be saturated or unsaturated. The aliphatic polybasic acid is preferably chain dibasic acid of carbon number 2 to 16. The particular examples include: ethanedioic acid, propanedioic acid, straight-chain type or branching type butanedioic acid, straight-chain type or branching type pentanedioic acid, straight-chain type or branching type hexanedioic acid, straight-chain type or branching type heptanedioic acid, straight-chain type or branching type octanedioic acid, straight-chain type or branching type nonanedioic acid, straight-chain type or branching type decanedioic acid, straight-chain type or branching type undecanedioic acid, straight-chain type or branching type dodecanedioic acid, straight-chain type or branching type tridecanedioic acid, straight-chain type or branching type tetradecanedioic acid, straight-chain type or branching type heptadecanedioic acid, straight-chain type or branching type hexadecanedioic acid, straight-chain type or branching type hexenedioic acid, straight-chain type or branching type heptenedioic acid, straight-chain type or branching type octanedioic acid, straight-chain type or branching type nonenedioic acid, straight-chain type or branching type decenedioic acid, straight-chain type or branching type undecenedioic acid, straight-chain type or branching type dodecenedioic acid, straight-chain type or branching type tridecenedioic acid, straight-chain type or branching type tetradecenedioic acid, straight-chain type or branching type heptadecenedioic acid, straight-chain type or branching type hexadecenedioic acid, alkenyl succinic acid, and mixtures thereof. On the other hand, examples of cyclic polybasic acid include alicyclic dicarboxylic acid such as 1,2-cyclohexane dicarboxylic acid and 4-cyclohexene-1,2-dicarboxylic acid, aromatic dicarboxylic acid such as phthalic acid and the like, tricarboxylic acid such as trimellitic acid and the like, aromatic tetracarboxylic acid such as pyromellitic acid.

(amine) Examples of amine include ammonia, monoamine, diamine, polyamine, and alkanolamine. In particular, the examples include: alkylamine having alkyl group of carbon number 1 to 30 (these alkyl groups may be straight-chain type or branching type.) such as methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, diundecylamine, didodecylamine, ditridecylamine, ditetradecylamine, dipentadecylamine, dihexadecylamine, diheptadecylamine, dioctadecylamine, methylethylamine, methyipropylamine, methylbutylamine, ethylpropylamine, ethylbuthylamine, and propylbutylamine; alkenylamine having alkenyl groups of carbon number 2 to 30 (these alkenyl groups may be straight-chain type or branching type.) such as ethenylamine, propenylamine, butenylamine, octenylamine, and oleylamine; alkylenediamine having alkylene groups of carbon number 1 to 30 such as methylenediamine, ethylenediamine, propylenediamine, and butylenediamine; polyamine such as diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine; the above monoamine, diamine, and polyamine substituted with alkyl groups or alkenyl groups of carbon number 8 to 20 such as undecyldiethylamine and oleylpropylenediamine; heterocyclic compounds such as N-hydroxyethyl oleylimidazoline; alkanol amines having alkanol groups of carbon number 1 to 30 (these alkanol groups may be straight-chain type or branching type.) such as methanolamine, ethanolamine, propanolamine, butanolamine, pentanolamine, hexanolamine, heptanolamine, octanolamine, nonanolamine, methanolethanolamine, methonolpropanolamine, methanolbutanolamine, ethanolpropanolamine, ethanolbutanolamine, and propanolamine, undecyldiethanolamine, dodecyldipropanolamine, oleyldiethanolamine; alkyleneoxide adduct of the above compounds; and mixtures thereof. Among these amines, primary amine, secondary amine, and alkanolamine are preferable.

The carbon number of hydrocarbon radical contained in such amines, is preferably 4 or more, more preferably 4 to 30, most preferably 8 to 18. When the carbon number of hydrocarbon radical of amine compounds is less than 4, the solubility tends to be deteriorated. Whereas, by setting the carbon number of amine compounds to be 30 or less, it becomes possible to relatively increase the content of molybdenum in the organomolybdemum compounds; addition of small amount of such amines can enhance the effect of the present invention.

(Amide)

Examples of amide include: amide obtained from the above-mentioned amine, in particularly, ammonia or aliphatic amine having either alkyl groups or alkenyl groups of carbon number 1 to 30, and saturated or unsaturated fatty acid of carbon number 1 to 30, and amide obtained from the above alkanolamine and saturated or unsaturated fatty acid of carbon number 1 to 30. More precisely, fatty acid amide such as laurylamide, myrustylamide, palmitylamide, oleylamide, stearylamide; alkanolamide such as lauryl diethanolamide, myrityl diethanolamide, palmityl diethanolamide, stearyl diethanolamide, oleyl diethanolamide can be the examples.

(Imide)

Examples of imide include succinicimide having alkyl groups or alkenyl groups of carbon number 4 or more. The succinicimides are, for example, succinicimides having alkyl groups or alkenyl groups of carbon number 4 to 30, preferably carbon number 8 to 18. When the carbon number of alkyl group or alkenyl group of such succinicimide is less than 4, the solubility tends to be deteriorated. Whereas, succinicimide having alkyl groups or alkenyl groups of carbon number over 30 and 400 or less can be used. By setting the carbon number of amine compounds to be 30 or less, it becomes possible to relatively increase the content of molybdenum in the molybdenum succinicimide complex; addition of small amount of such amines can enhance the effect of the present invention.

(Compounds Having Alcoholic Hydroxyl Group)

Compounds having alcoholic hydroxyl group may be any one of compounds selected from the group consisting of: monovalent alcohol, polyvalent alcohol, partial ester compounds or partial ether compounds of the polyvalent alcohol.

As monovalent alcohol, normally alcohol of carbon number 1 to 24, preferably carbon number 1 to 12, more preferably carbon number 1 to 8 can be used. These alcohols may be straight-chain type or branching type, and may be saturated or unsaturated. Examples of alcohol of carbon number 1 to 24, particularly, methanol, ethanol, straight-chain type or branching type propanol, straight-chain type or branching type butanol, straight-chain type or branching type pentanol, straight-chain type or branching type hexanol, straight-chain type or branching type heptanol, straight-chain type or branching type octanol, straight-chain type or branching type nonanol, straight-chain type or branching type decanol, straight-chain type or branching type undecanol, straight-chain type or branching type dodecanol, straight-chain type or branching type tridecanol, straight-chain type or branching type tetradecanol, straight-chain type or branching type pentadecanol, straight-chain type or branching type hexadecanol, straight-chain type or branching type heptadecanol, straight-chain type or branching type octadecanol, straight-chain type or branching type nonadecanol, straight-chain type or branching type icosanol, straight-chain type or branching type henicosanol, straight-chain type or branching type tricosanol, straight-chain type or branching type tetracosanol, and mixtures thereof and the like.

On the other hand, as polyvalent alcohol, normally divalent to decavalent, preferably divalent to hexavalent of such alcohol can be used. Examples of divalent to decavalent polyvalent alcohol, particularly: divalent alcohols such as ethyleneglycol, diethyleneglycol, polyethyleneglycol (trimer to pentadecamer of ethyleneglycol), propyleneglycol, dipropyleneglycol, polypropyleneglycol (trimer to pentadecamer of polypropyleneglycol) 1,3-propanediol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,2-propanediol, 2-methyl-1,3-propanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, neopentylgrycol; polyvalent alcohols such as glycerin, polyglycerin (dimmer to octamer of glycerin: e.g., diglycerin, triglycerin, tetraglycerin) , trimethylol alkane (such as trimethylol ethane, trimethylol propane, trimethylol butane) and dimmer to octamer thereof, pentaerythritol and dimmer to tetramer thereof, 1,2,4-butanetriol, 1,3,5-pentane triol, 1,2,6-hexanetriol, 1,2,3,4-butanetetrol, sorbitol, sorbitan, sorbitol glycerin condensation, adonitol, arabitol, xylitol, mannitol; sugar group such as xylose, arabinose, ribose, rhamnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose, sucrose; and mixtures thereof.

Examples of partial ester of polyvalent alcohol include compounds such that a part of hydroxyl group contained in the polyvalent alcohol shown in the above description is esterified with a hydrocarbyl group. Among such compounds, glycerin monoolate, glycerin dioleate, sorbitan monooleate, sorbitan dioleate are preferable.

Also, examples of partial ether of polyvalent alcohol include compounds such that a part of hydroxyl group contain in the polyvalent alcohol shown in the above description is etherified with a hydrocarbyl group, and compounds (like sorbitan condensate) such that ether bonds are formed by condensation between polyvalent alcohols.

(Tetra- to hexa-valent molybdenum compounds) Examples of molybdenum compounds include molybdenum trioxide or hydrate thereof (MoO₃.nH₂O), molybdic acid (H₂MoO₄), alkali metal salt of molybdic acids (M₂MoO₄; M represents alkali metal salt.), ammonium molybdate ((NH₄)₂MoO₄ or (NH₄)₆[Mo₇O₂₄].4H₂O) , MoCl₆, MoOCl₄, MoO₂Cl₂, MoO₂Br₂, Mo₂O₃Cl₆. Among such molybdenum compounds, from the view point of yield of the intended compound, tetra- to hexa-valent molybdenum compounds are preferable, and hexa-valent molybdenum compounds are particularly preferable. Further, from the view point of (commercial) availability, among such hexa-valent molybdenum compounds, molybdenum trioxide or hydrate thereof, molybdic acids, alkali metal salt of molybdic acids, and ammonium molybdate are preferable.

The organomolybdenum compounds of the invention can be particularly obtained as molybdenum salt of organic acids, molybdenum amine complex, alcohol molybdenum salt, and the like. Also, when molybdic acid as a strong acid is reacted with compounds having alcoholic hydroxyl group, molybdic acid alcohol ester can be obtained.

Preferable examples of organomolybdenum compounds of the invention particularly include:

(a) a salt of at least a kind of acid containing phosphorus selected from a group consisting of: phosphite monoester, phosphate monoester, phosphite diester, phosphate diester, phosphonous acid, phosphonic acid, phosphonous acid monoester, and phosphonic acid monoester, respectively having at least an alkyl group of carbon number 3 to 30, with molybdenum compounds;

(b) a complex of a kind of amine compound selected from a group consisting of: primary amine, secondary amine, and alkanolamine, respectively having at least an alkyl group or an alkenyl group of carbon number 3 to 30, with molybdenum compounds;

(c) a salt or an ester of alcohols having at least an alcoholic hydroxyl group selected from a group consisting of: monovalent alcoholes, polyvalent alcohols, and partial ester or partial ether of the polyvalent alcohols of carbon number 3 to 30, with molybdenum compounds;

(d) a salt or an ester of amide compounds having at least an alkyl group or an alkenyl group of carbon number 3 to 30 and alcoholic hydroxyl groups, with molybdenum compounds; and

(e) a salt of fatty acids of carbon number 3 to 30 with molybdenum compounds.

Other than the above examples, as the organomolybdenum compounds, molybdenum dithiocarbamic acids such as oxymolybdenum dithiocarbamate, sulfurized molybdenum dithiocarbamate, and sulfurized oxymolybdenum dithiocarbamate; molybdenum dithiophosphates such as oxymolybdenum dithiophosphate, sulfurized molybdenum dithiophosphate, and sulfurized oxymolybdenum dithiophosphate can be used. When the above examples are used at the same time with borate ester and/or derivatives thereof, borated alkyl or alkenyl succinimide, these of which will be described later, the effect of corrosion or corrosive wear of metallic material containing lead caused by the use with such boron compounds can be expected. Therefore the above examples can be used. On the other hand, when the above examples are not used at the same time with borate ester and/or derivatives thereof, borated alkyl or alkenyl succinimide, molybdenum dithiophosphate is excluded.

In the lubricant composition of the invention, one kind of or two or more kinds of the above-mentioned organomolybdenum compounds may be used. The content is, for total amount of the lubricant composition, preferably 10 ppm by mass or more, more preferably 30 ppm by mass or more, further preferably 100 ppm by mass or more; it is also preferably 1000 ppm by mass or less, more preferably 600 ppm by mass or less, further preferably 400 ppm by mass or less, based on the molybdenum element conversion. When the content of organomolybdenum compounds is less than 10 ppm by mass based on the molybdenum element conversion, corrosion inhibiting performance is not sufficiently produced; when the content is over 1000 ppm by mass, the positive effect cannot be sufficiently obtained in proportion to the increase of content.

<Borate Ester>

An embodiment of the lubricant composition of the invention includes borate ester and/or derivatives thereof. In general, borate ester is normally used as a corrosion inhibiting agent for bearing at the same time with sulfur and/or phosphorus compound (e.g., Japanese Patent Application Laid-Open (JP-A) No. 63-304095, JP-A No. 63-304096, JP-A No. 2000-63865, JP-A No. 2000-63871) Recently, it is found out that borate ester also has an effect to raise friction coefficient of metal-to-metal contact (JP-A No. 2002-226882).

Examples of borate ester of the invention include compounds represented by the general formula (4) or (5) shown below and the derivatives thereof.

In the general formulas (4) and (5), R¹¹˜R¹⁶ indicate hydrocarbon radicals of carbon number 1 to 30. The R¹¹˜R¹⁶ may be the same or different from each other.

Examples of the above hydrocarbon radicals of carbon number 1 to 30 particularly include: alkyl groups of carbon number 1 to 30 (these alkyl groups may be straight-chain type or branching type.) such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, and octadecyl group; alkenyl groups of carbon number 2 to 30 (these alkenyl groups may be straight-chain type or branching type.) such as ethenyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, tridecenyl group, tetradecenyl group, pentadecenyl group, hexadecenyl group, heptadecenyl group, octadecenyl group; cycloalkyl groups of carbon number 5 to 7 such as cyclopentyl group, cyclohexyl group, and cycloheptyl group; alkyl cycloalkyl group of carbon number 6 to 11 (substitution sites of alkyl groups to the cycloalkyl groups are optional.) such as methyl cyclopentyl group, dimethyl cyclopentyl group, methylethyl cyclopentyl group, diethyl cyclopentyl group, methyl cyclohexyl group, dimethyl cyclohexyl group, methylethyl cyclohexyl group, diethyl cyclohexyl group, methylcycloheptyl group, dimethyl cycloheptyl group, methylethyl cycloheptyl group, diethyl cycloheptyl group; aryl groups of carbon number 6 to 18 such as phenyl group, naphthyl group; alkylaryl groups of carbon number 7 to 26 (these alkyl groups may be straight-chain type or branching type; substitution sites to the aryl groups are optional.) such as tolyl group, xylyl group, ethylphenyl group, propylphenyl group, butylphenyl group, pentylphenyl group, hexylphenyl group, heptylphenyl group, octylphenyl group, nonylphenyl group, decyiphenyl group, undecylphenyl group, dodecylphenyl group, diethylphenyl group, dibutylphenyl group, and dioctylphenyl group; arylalkyl groups of carbon number 7 to 12 (alkyl groups may be straight-chain type or branching type.) such as benzyl group, phenylethyl group, phenylpropyl group, phenylbutyl group, phenylpentyl group, phenylhexyl group.

The above hydrocarbon radicals of carbon number 1 to 30 are preferably hydrocarbon radicals of carbon number 2 to 24, more preferably that of carbon number 3 to 20; more particularly, these are preferably alkyl groups of carbon number 1 to 30 or aryl groups of carbon number 6 to 24, more preferably alkyl groups of carbon number 3 to 18, furthermore preferably, that of carbon number 4 to 12.

The borate ester represented by the general formula (4) can be normally obtained by reacting 3 moles of alcohols of carbon number 1 to 30 with 1 mole of orthoboric acid (H₃BO3)

The borate ester represented by the general formula (5) can be normally obtained by reacting 1 mole of alcohols of carbon number 1 to 30 with 1 mole of orthoboric acid (H₃BO₃)

Reaction condition of the above reactions are not particularly limited. It is particularly preferable to carry out the reaction at 100° C. or more, because this condition enables to remove generating water at the same time.

As the derivatives of borate ester, the examples include organoborate compounds described in Japanese Patent Application Laid-Open No. 2002-226882 and among them, compounds in which phosphorus and sulfur are not contained. The examples are organoborate polyamine condensate (condensate of polyamine and the above borate ester), and organoborate polyol condensate condensate of polyol and the above borate ester).

Preferable examples of borate ester and derivatives thereof particularly include such as triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-n-butyl borate, tri-sec-butyl borate, tri-tert-butyl borate, trihexyl borate, trioctyl borate, tridecyl borate, tridodecyl borate, trihexadecyl borate, trioctadecyl borate, triphenyl borate, tribenzyl borate, triphenethyl borate, tritolyl borate, triethylphenyl borate, tripropylphenyl borate, tributylphenyl borate, and trinonylphenyl borate. Among these, tri-n-butyl borate, trioctyl borate, tridodecyl borate are particularly preferable.

In the lubricant composition of the invention, lower limit of the content of borate ester or derivatives thereof is, from the view point of corrosion inhibition or corrosive-wear inhibition of metallic materials containing lead, for total amount of composition, 0.001% by mass or more, preferably 0.1% by mass or more in terms of boron. Whereas, upper limit of the content of borate ester or derivatives thereof is, for total amount of composition, 0.1% by mass or less, preferably 0.08% by mass or less in terms of boron. When the content of borate ester or derivatives thereof becomes over the above upper limit, the anti-wear effect cannot be sufficiently obtained in proportion to the increase of content. Therefore, overwhelming the upper limit is not preferable. In the lubricant composition of the invention, when the borate esters are used at the same time with the above-mentioned organomolybdenum compounds, from the view point of corrosion inhibition or corrosive-wear inhibition of metallic materials containing lead, the content of borate esters may be preferably 0.04% by mass or less, more preferably 0.02% by mass or less. In addition, in the invention, when zinc dithiophosphate is not added, or phosphorus compounds other than this are not substantially added together with zinc dithiophosphate (i.e., no phosphorus contained), for the purpose of improving anti-wear performance, it is desirable that borate ester or derivatives thereof are made to contain preferably more than 0.05% by mass or more, more preferably 0.06% by mass or more.

<Borated alkyl or alkenyl Succinimide>

An embodiment of the lubricant composition of the invention contains modified alkyl or alkenyl borate succinimide. The wording “modified alkyl or alkenyl borate succinimide” means “modified alkyl borate succinimide” or “modified alkenyl borate succinimide” (hereinafter, same as the above meaning in the present specification.). The alkyl or alkenyl succinimide to be used are, for instance, monoimide represented by the following formula (6) and bisimide represented by the formula (7). In this invention, compounds which are obtained by modifying these imides with boric acid can be the examples.

In the formulas (6) and (7), R¹⁷, R18, and R¹⁹ respectively indicate alkyl groups or polyalkenyl groups; a and b respectively indicate integer number 2 to 5.

Number average molecular weight of alkyl group or polyalkenyl group represented by the above R¹⁷ R¹⁸, and R¹⁹ are preferably 100 or more, more preferably 700 or more, furthermore preferably 1000 or more, particularly preferably 1200 or more. It is also, preferably 3500 or less, more preferably 2000 or less, furthermore preferably 1500 or less. Also, a and b are preferably 3 or 4, respectively.

R¹⁷, R¹⁸, and R¹⁹ are preferably polybutenyl groups. Polybutenyl group means polybutene which can be obtained by polymerizing mixture of 1-butene and isobutene, or polymerizing high-purity isobutene with alminum chloride series or boron fluoride series catalyst. The catalyst of which trace amount of fluoride or chlorine is fully removed can be also preferably used.

Production method of succinimide is not particularly limited. For example, it can be obtained as follows. Chlorinated polybutene of number average molecular weight 800 to 3500, preferably polybutene whose chloride and fluorine are fully removed, is reacted with maleic anhydride between 100° C. and 200° C. to obtain polybutenyl succinic acid. Then, the polybutenyl succinic acid is reacted with polyamine to obtain the desired succinimide. Examples of polyamine include diethylene triamine, triethylene tetramine, tetraethylene pentamine, and pentaethylene hexamine.

Production methods of modified borate succinimide are, for example, methods disclosed in Japanese Patent Application Laid-Open (JP-A) No. 42-8013, JP-A No. 42-8014, JP-A No. 51-52381, JP-A No. 51-130408, and etc. In particular, polyamine and alkyl or polyalkenyl succinic acid (anhydride) are added to the organic solvent, light lubricant base oil, and the like such as alcohols, hexane, and xylene; boron compounds such as boric acid, borate ester, or borate salt are added thereto; these are mixed and treated with heat under a suitable condition so as to obtain the modified borate succinimide. The content of boric acid in such modified alkyl borate succinimide obtained by the above method can be normally 0.1˜4.0% by mass.

In the lubricant composition of the invention, one kind of the above modified alkyl or alkenyl borate succinimide may be used, but also two or more thereof may be used in combination with each other. The amount thereof is, for total amount of composition, the lower limit is preferably 0.01% by mass, more preferably 0.05% by mass, furthermore preferably 0.07% by mass based on the nitrogen element reduced quantity. On the other hand, the upper limit is, for total amount of composition, 0.4% by mass, preferably 0.3% by mass based on the nitrogen element reduced quantity. When the content of modified alkyl or alkenyl borate succinimide is less than 0.01% by mass, even though the lubricant composition contains organomolybdenum compounds, inhibition of corrosion or corrosive wear is insufficient. Whereas, when the content of over 0.4% by mass is not preferable as it does not show sufficient performance in proportion to the increase of contents.

The content of the above modified alkyl or alkenyl borate succinimide as a boron element reduced quantity is not particularly limited. Nevertheless, for total amount of said lubricant composition, it is preferable to contain 0.005% by mass or more of boron, more preferably 0.01% by mass or more, further preferably 0.02% by mass or more, furthermore preferably 0.04% by mass or more, particularly preferably 0.05% by mass or more. When the content of modified alkyl or alkenyl borate succinimide as a boron element reduced quantity becomes large, there is fear of negative influence to the seals and of increase of sulfated ash. Therefore, the content of boron is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, further preferably 0.08% by mass or less. Mass ratio (Mo/B ratio) between the amount of molybdenum element of the above organomolybdenum compounds and the amount of boron element of modified alkyl or alkenyl borate succinimide is not particularly limited. It is preferably 0.1 or more, more preferably 0.2 or more, further preferably 0.4 or more, particularly preferably 1 or more. Since it is difficult to obtain sufficient effect in proportion with the content of organomolybdenum compounds, the ratio is also preferably 5 or less, more preferably 3 or less, particularly preferably 1.5 or less.

Other than the above components, the lubricant composition of the invention preferably contains one or more kinds of component selected from the group consisting of antioxidant, anti-wear agent other than zinc dithiophosphate, and metallic detergent. It will be respectively described as follows.

<Antioxidant>

To the lubricant composition of the invention, it is preferable to add antioxidant. As the antioxidant, examples include ashless antioxidant such as phenolic antioxidant and amine antioxidant, and organometallic antioxidant; antioxidant which is generally used for lubricant can be used. By adding such antioxidant, it is possible to inhibit the generation and accumulation of deteriorated component of the lubricant composition. That can enhance the corrosion or corrosive-wear inhibiting performance of the composition of the invention against metals containing copper-lead, but also enhance the property of base number preservation further more.

As phenolic antioxidant, 4,4′-methylenebis(2,6-di-tert-butylphenol), 4,4′-bis (2,6-di-tert-butylphenol), 4,4′-bis (2-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 4,4′-isopropylidenebis (2,6-di-tert-butylphenol), 2,2′-methylenebis (4-methyl-6-nonylphenol), 2,2′-isobutylidenebis (4,6-dimethylphenol), 2,2′-methylenebis (4-methyl-6-cyclohexylphenol), 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-α-dimethylamino-p-cresol, 2,6-di-tert-butyl-4-(N,N′-dimethylaminomethylphenol), 4,4′-thiobis (2-methyl-6-tert-butylphenol), 4,4′-thiobis (3-methyl-6-tert-butylphenol), 2,2′-thiobis (4-methyl-6-tert-butylphenol), bis(3-methyl-4-hydroxy-5-tert-butylbenzyl)sulfide, bis(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide, 2,2′-thio-diethylenebis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], tridecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, pentaerythrityl-tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 3-methyl-5-tert-butyl-4-hydroxyphenyl substitution fatty acid esters, can be the preferable examples. These may be used in combination with two or more thereof.

Examples of amine antioxidant include phenyl-α-naphthylamine, alkylphenyl-α-naphthylamine, and dialkyl diphenylamine. These may be used in combination with two or more thereof.

The above phenolic antioxidant, amine antioxidant, and organometallic antioxidant can be mixed in combination with each other.

In case that antioxidant is added in the lubricant composition, amount thereof is, for total amount of the lubricant composition, normally 20% by mass or less, preferably 10% by mass or less, further preferably 5% by mass or less. When the content is over 20% by mass, sufficient performance can not be obtained in proportion with the mixing amount, therefore such content is not preferable. On the other hand, as it can be possible to preserve the corrosion or corrosive-wear inhibiting performance of metallic material containing copper-lead for long period, the content is preferably 0.1% by mass or more, more preferably 1% by mass or more, particularly preferably 1.5% by mass or more.

<Anti-Wear Agent Other than Zinc Dithiophosphate>

As the anti-wear agent other than zinc dithiophosphate, examples include phosphorus anti-wear agent other than zinc dithiophosphate, sulfur anti-wear agent, or boron anti-wear agent; any kind of anti-wear agent which is generally used for lubricant can be used.

Phosphorus anti-wear agent is not particularly limited as long as it is an anti-wear agent containing phosphorus in the molecules. The phosphorus anti-wear agent in the invention, it is preferably at least any one kind of compound selected from the group consisting of phosphorus compounds represented by the general formula (8), phosphorus compounds represented by the general formula (9), and metal salt thereof or amine salt thereof, or derivatives thereof.

In formula (8), X¹, X², and X³ respectively indicate oxigen atom or sulfur atom, R²⁰, R²¹, and R²² respectively indicate hydrogen atom or hydrocarbon radicals of carbon number 1 to 30.

In formula (9), X⁴, X⁵, X⁶, and X⁷ respectively indicate oxygen atom or sulfur atom (one or two of X⁴, X⁵, and X⁶ may be single bond or (poly) oxyalkylene group.). R²³, R²⁴, and R²⁵ respectively indicate hydrogen atom or hydrocarbon radicals of carbon number 1 to 30.

Examples of the above hydrocarbon radicals of carbon number 1 to 30 represented by R²⁰˜R²⁵ include alkyl group, cycloalkyl group, alkenyl group, alkyl substitution cycloalkyl group, aryl group, alkyl substitution aryl group, and arylalkyl group. Particularly, the hydrocarbon radicals can be the same substitution group of R⁵˜R¹⁰ of the above general formulas (2) and (3).

The above hydrocarbon radicals of carbon number 1 to 30 represented by R²⁰˜R²⁵ are preferably alkyl groups of carbon number 1 to 30 or aryl groups of carbon number 6 to 24, more preferably alkyl groups of carbon number 3 to 18, furthermore preferably alkyl groups of carbon number 4 to 12.

The phosphorus compounds represented by the general formula (8) can be the examples of the following phosphorus compounds: phosphite, monothiophosphite, dithiophosphite, trithiophosphite; phosphite monoester, monothiophosphite monoester, dithiophosphite monoester, trithiophosphite monoester respectively having an above hydrocarbon radical of carbon number 1 to 30; phosphite diester, monothiophosphite diester, dithiophosphite diester, trithiophosphite diester respectively having two above hydrocarbon radicals of carbon number 1 to 30; phosphite triester, monothiophosphite triester, dithiophosphite triester, trithiophosphite trimester respectively having tree above hydrocarbon radicals of carbon number 1 to 30; and the mixture thereof.

In the invention, in order to improve corrosion or corrosive-wear inhibiting property of copper and to enhance long-drain performance such as high-temperature detergency, oxidative stability, and base number preservation property, among X¹˜X³of general formula (8), preferably two or more of them are oxygen atoms, particularly preferably all of them are oxygen atoms.

Examples of phosphoric compound represented by the general formula (9) can be as follows: phosphate, monothio phosphate, dithio phosphate, trithio phosphate, tetrathio phosphate; phosphate monoester, monothiophosphate monoester, dithiophosphate monoester, trithiophosphate monoester, tetrathiophosphate monoester respectively having one of the above hydrocarbon radicals of carbon number 1 to 30; phosphate diester, monothiophosphate diester, dithiophosphate diester, trithiophosphate diester, tetrathiophosphate diester respectively having two of the above hydrocarbon radicals of carbon number 1 to 30; phosphate triester, monothiophosphate triester, dithiophosphate triester, trithiophosphate triester, tetrathiophosphate trimester respectively having three of the above hydrocarbon radicals of carbon number 1 to 30; phosphonic acid, phosphonic acid monoester, phosphonic acid diester respectively having one to three of the above hydrocarbon radicals of carbon number 1 to 30; the above phosphorus compounds having (poly) oxyalkylene groups of carbon number 1 to 4; derivatives of the above phosphorus compound such as reactant of β-dithiophosphorylised propionic acid or dithiophosphoric acid and olefin cyclopentadien or (methyl)methacrylate; and mixtures thereof.

In the invention, in order to improve corrosion or corrosive-wear inhibiting property of copper and to enhance long drain performance such as high-temperature detergency, oxidative stability, and base number preservation property, among X⁴˜X⁷ of general formula (9), preferably two or more of them are oxygen atoms, preferably three or more of them are oxygen atoms, particularly preferably all of them are oxygen atoms. One or two of X⁴, X⁵, and X⁶ may be single bond or (poly)oxyalkylene group.

Examples of phosphorus compounds salt represented by the general formula (8) or (9) include salt obtained by that phosphorus compounds is reacted with nitrogen compounds such as amine compounds whose molecules only contain: metal base such as metal-oxide, metal hydroxide, metal carboxylate, metal chloride; ammonia; hydrocarbon radicals of carbon number 1 to 30; or hydrocarbon radicals containing hydroxyl group of carbon number 1 to 30, and neutralize a part or all of remaining acidic hydrogen.

Examples of metal of the above metal base particularly include: alkali metals such as lithium, sodium, potassium, and cesium; alkali earth metals such as calcium, magnesium, barium; heavy metals such as zinc, copper, iron, lead, nickel, silver, manganese. Among these, alkali earth metals such as calcium and magnesium, as well as zinc are preferable.

Metal salts of the above phosphorus compound are structually different depend on the valence of metal and number of OH— (hydroxyl) group or SH— (sulfhydryl) group in a phosphorus compound, therefore the structure is not particularly limited. For instance, when 1 mole of zinc oxide and 2 moles of phosphate diester (having one OR— group) are reacted, a compound having a structure represented by the following general formula (10) is assumed to be obtained as the main component. However, polymerized molecules are also assumed to exist at the same time.

In addition, for example, when 1 mole of zinc oxide and 1 mole of phosphate monoester (having two OH— groups) are reacted, a compound having a structure represented by the following general formula (11) is assumed to be obtained as the main component. However, polymerized molecules are also assumed to exist at the same time.

Examples of the above nitrogen compounds particularly include ammonia, monoamine, diamine, polyamine. More particularly, amine compounds constituting the above molybdenum amine complex of the organomolybdenum compounds can be the similar examples.

Among such nitrogen compounds, aliphatic amine having alkyl group or alkenyl group of carbon number 10 to 20 (these may be straight-chain type or branching type.) such as decylamine, dodecylamine, dimethyldodecylamine, tridecylamine, heptadecylamine, octadecylamine, oleylamine, and stearylamine can be the preferable examples.

As the phosphorus anti-wear agent, at least one kind of compound selected from a group consisting of: phosphorus compound metal salt of general formula (8) whose X¹, X², and X³ are all oxygen atoms; and phosphorus compound metal salt of general formula (9) whose X⁴, X⁵, X⁶, and X⁷ are all oxygen atoms (any one or two of X⁴, X⁵, and X⁶ may be single bonds or (poly) oxyalkylene groups) is preferable from the view point of excellent long drain performance such as oxidation stability, high-temperature detergency, and of excellent low-friction property. F

Further, when the phosphorus anti-wear agent is a phosphorus compound metal salt of general formula (9) whose X⁴, X⁵, X⁶, and X⁷ are all oxygen atoms (any one or two of X⁴, X⁵, and X⁶ may be single bonds or (poly)oxyalkylene groups) , and whose R²³, R²⁴, and R²⁵ are respectively hydrocarbon radicals of carbon number 1 to 30, the agent becomes excellent in long drain performance such as oxidation stability, high-temperature detergency, moreover, excellent in low-friction property and low-ash property.

Among such components, preferable components are as follows: salt of zinc or calcium and phosphite diester having two alkyl groups or two aryl groups of carbon number 3 to 18; phosphite trimester having three alkyl groups or aryl groups of carbon number 3 to 18, preferably having three alkyl groups of carbon number 6 to 12; salt of zinc or calcium and phosphate monoester having an alkyl group or aryl group of carbon number 3 to 18; salt of zinc or calcium and phosphate diester having two alkyl groups or aryl groups of carbon number 3 to 18; salt of zinc or calcium and phosphonate monoester having two alkyl groups or aryl groups of carbon number 1 to 18; phosphate triester having three alkyl groups or aryl groups of carbon number 3 to 18, preferably three alkyl groups of carbon number 6 to 12; phosphonate diester having three alkyl groups or aryl groups of carbon number 1 to 18. These components may be used alone or in combination with two or more thereof.

In the lubricant composition of the invention, content of the above phosphorus anti-wear agent is not particularly limited. However, for total amount of composition, it is 0.005% by mass or more, preferably 0.01% by mass or more, particularly preferably 0.02% by mass or more in terms of phosphorus. The content is also preferably 0.1% by mass or less, more preferably 0.08% by mass or less, particularly preferably 0.05% by mass or less. When the content of phosphorus anti-wear agent is less than 0.005% by mass as phosphorus element, anti-wear property is not effective, thus the content is not preferable. On the other hand, when the content is over 0.1% by mass as phosphorus element, there is a fear that adverse influence to the exhaust-gas aftertreatment device can be considered, thus it is not preferable. While, as phosphorus anti-wear agent, when sulfur-phosphorus anti-wear agent such as zinc dithiophosphate are to be added, from the view point of inhibiting corrosion or corrosive-wear of copper, content of the above agents are, for total amount of the composition, 0.06% by mass or less, preferably 0.05% by mass or less, further preferably 0.04% by mass or less, or 0% by mass based on phosphorus element reduced quantity, so as to produce a low-sulfur and long-draine4 lubricant composition.

Examples of sulfur anti-wear agent include sulfur compounds such as disulfide, sulfurized olefin, sulfurized fat, dithiocarbamate, zinc dithiocarbamate. These sulfur compounds can be suitably added in order to inhibit corrosion or corrosive-wear. When the content is 0.15% by mass or less, preferably 0.1% by mass or less, particularly 0.05% by mass or less, or 0% by mass, a low-sulfur and long-drain lubricant composition can be produced.

<Metallic Detergent >

The lubricant composition of the invention preferably contains metallic detergent. Examples of metallic detergent include sulfonate series detergent, pheinate series detergent, salicylate series detergent, carboxylate series detergent.

As the sulfonate series detergent, particularly, for example, alkyl aromatic sulfonic acid metal salts obtained by sulfonating alkyl aromatic compounds of molecular weight 100 to 1500, preferably 200 to 700 are preferably used. Among such metal salt, preferably alkali earth metal salt, particularly magnesium salt and/or calcium salt are preferably used. Also, examples of alkyl aromatic sulfonic acid include the so-called “petroleum sulfonate” and “synthetic sulfonate”.

As the petroleum sulfonate, generally, compounds obtained by sulfonating alkyl aromatic compounds in the lubricant fraction of mineral oil, or the so-called “mahogany acid” obtained as by-product during the white oil production are used. Also, as the synthetic sulfonate, compounds obtained from alkylbenzene production plant for producing raw material of detergent as a by-product can be used. Or, sulfonated alkyl benzene having straight-chain type or branching type alkyl group obtained by alkylating benzene with polyolefin or sulfonated dinonylnaphthalene can be used. Sulfonating agent for sulfonating the above alkyl aromatic compounds are not particularly limited, usually, fuming sulfuric acid and sulfuric acid can be used.

Examples of alkali earth metal sulfonate include compounds represented by the following general formula (12) or (13).

In the formulas: R²⁶ and R²⁷ may be the same or different from each other, each of them indicates straight-chain type or branching type alkyl groups of carbon number 4 to 30, preferably 8 to 25; M¹ indicates alkali earth metal, preferably calcium and/or magnesium.

Examples of phenate series detergent particularly include: alkylphenol having at least one straight-chain type or branching alkyl group of carbon number 4 to 30, preferably carbon number 6 to 18; alkylphenol sulfide metal salt obtained by reacting this alkylphenol with elementary sulfur; or metal salt of alkylphenol's Mannich reaction product obtained by reacting this alkylphenol with formaldehyde, preferably alkali earth metal salt, particularly preferably magnesium salt and/or calcium salt and the like.

Examples of alkali earth metal phenate include compounds represented by the following general formulas (14)˜(16).

In the formulas: R²⁸, R²⁹, R³⁰, R³¹, R³² and R³³ may be the same or different from each other, each of them indicates straight-chain type or branching type alkyl group of carbon number 4 to 30, preferably 6 to 18; M², M³, and M⁴ respectively indicate alkali earth metal, preferably calcium and/or magnesium; x indicates integer number 1 or 2.

Examples of salicylate series detergent particularly include alkyl salicylic acid metal salt having at least a straight-chain type or branching type alkyl group of carbon number 4 to 32, preferably carbon number 6 to 19, or carbon number 20 to 30; among these, it is preferably alkali earth metal salt, particularly preferably magnesium salt and/or calcium salt.

As alkali earth metal salicylate, for example, a compound represented by the following general formula (17) can be used.

In the formula, R³⁴ and ³⁵ may be the same or different from each other, each of them indicates hydrogen or straight-chain type or branching type alkyl groups of carbon number 1 to 32, at least either one of R³⁴ and R³⁵ is straight-chain type or branching type alkyl groups of carbon number 8 to 32, preferably carbon number 14 to 32; M⁵ indicates alkali earth metal, preferably calcium and/or magnesium. As the alkali earth metal salicylate, an alkali earth metal salicylate in which either one of R³⁴ and R³⁵ is hydrogen, and another one is secondary alkyl group induced from straight-chain type a-olefin of carbon number 14 to 32, preferably carbon number 14 to 19 or carbon number 20 to 30, is preferable. [01501 Examples of alkali earth metal sulfonate detergent, alkali earth metal phenate detergent, and alkali earth metal salicylate detergent include: neutral salt (normal salt) that can be obtained by that alkyl aromatic sulfonic acid, alkylphenol, alkylphenol sulfide, product of alkylphenol by Mannich reaction, alkyl salicylic acid and the like are directly reacted with alkali earth metal base like alkali earth metal oxide and alkali earth metal hydroxide of magnesium and/or calcium. The neutral salt can also be obtained by once alkali metal salt such as sodium salt and potassium salt is made, then the alkali metal is substituted into alkali earth metal. The examples further include: basic salt obtained by that the above neutral salt (normal salt) and excess alkali earth metal salt or alkali earth metal base (hydroxide or oxide of alkali earth metal) are heated under the existence of water; and per-basic salt (hyper-basic salt) obtained by that the neutral salt (normal salt) is reacted with base such as hydroxide of alkali metal or alkali earth metal under the existence of carbon dioxide gas, boric acid, or borate.

These reactions are normally carried out in the solvent (aliphatic hydrocarbon solvent like hexane, aromatic hydrocarbon solvent like xylene, light lubricant, etc.). Metallic detergent is normally sold in the diluted form with such as light lubricant and thus available. If such metallic detergent is used, content of the metal is desirably from 1.0˜20% by mass, preferably 2.0˜16% by mass.

Metal ratio of these metallic detergent is not particularly limited, it is normally 1 to 40. However, in the invention, from the view point of easier inhibition of corrosion or corrosive-wear of lead, it is preferable to mix at least one kind of agent which metal ratio is preferably 2 or more, more preferably 2.6 or more. Further, from the view point of stability, the metal ratio is preferably 20 or less, more preferably 15 or less.

As a metallic detergent of the invention, because of its superior base number preservation property, an alkali earth metal salicylate is preferably used. In an example, alkali earth metal salicylate, which contains 85% by mole or preferably 90% by mole of alkali earth metal salicylate (monoalkyl type) having one secondary alkyl group induced from straight-chain type α-olefins of carbon number 14 to 19 which influence negatively on the corrosion or corrosive-wear of lead, is used. When such alkali earth metal salicylate is used, corrosion or corrosive-wear of lead is dramatically improved by using organomolybdenum compounds at the same time. Therefore, base number preservation property and inhibition of corrosion or corrosive-wear of lead can be compatible. The metal ratio of the alkali earth metal salicylate in such a case is desirably from 1.5 to 15, preferably from 2.6 to 5.

As a metallic detergent of the invention, since it is possible to inhibit further more corrosion or corrosive-wear of lead than the conventional agent, an alkali earth metal sulfonate of metal ratio 1 to 20, preferably 5 to 15, is preferably used. In order to enhance the base number preservation property, if necessary, use of the above alkali earth metal salicylate of metal ratio 1.5 or less, preferably 1.3 or less at the same time is preferable. In such a case, if alkali earth metal salicylate of metal ratio 1.5 or less is used, it is possible to obtain a composition also having excellent storage stability.

The metal rate can be represented by a formula: (valence of metal element in metallic detergent)×(content of metal element(% by mole))/(content of soap(% by mole)).

The soap means salicylic acid soap, sulfonic acid soap, and the like.

In the lubricant composition of the invention, when metallic detergent is added, the content is not particularly limited. Normally, for total amount of lubricant composition, the metal content is 0.01% by mass or more, preferably 0.05% by mass or more, furthermore preferably 0.1% by mass or more. In order to reduce the sulfated ash in the composition, it is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, furthermore preferably 0.2% by mass or less.

<Other Additives >

The lubricant composition of the invention is a composition which can inhibit corrosion or corrosive-wear of metals containing lead because of the above constitution. So as to improve the performance or to use for the other purpose, optional additives, which is generally used to lubricant, can be used. As such additives, for example, additives such as ashless dispersant other than the above borated alkenyl succinimide, friction modifier, viscosity index improver, corrosion inhibiting agent, rust inhibitor, anti-emulsifying agent, metal deactivator, defoamant, and coloring agent, can be used.

As ashless dispersant other than modified alkyl or alkenyl borate succinimde, optional ashless dispersant used for lubricant can be used. The examples are nitrogen compounds having at least one straight-chain type or branching type alkyl groups or alkenyl groups of carbon number 40 to 400 in the molecule, or derivatives thereof. The examples of nitrogen compound include succinimide, benzylamine, polyamine, Mannich-base. And the derivatives include derivatives that the above nitrogen compounds are reacted with compounds such as boron compound (other than modified alkyl or alkenyl borate succinimde) such as boric acid and borate; prosphorus compound such as (thio) phosphoric acid, (thio) phosphate; organic acid; hydroxyl (poly) oxyalkylene carbonate. In the invention, one or more kind of compounds randomly selected from the above compounds can be mixed. The alkyl group or alkenyl group has carbon number 40 to 400, preferably 60 to 350. When the carbon number of alkyl group or alkenyl group is less than 40, the solubility of the compound to the lubricant base oil declines; whereas, the carbon number of alkyl group or alkenyl group is over 400, low-temperature fluidity is deteriorated. Thus both of the cases are not preferable. Such alkyl groups oralkenyl groups maybe straight-chain type or branching type, particularly preferably, branching type alkyl group or branching type alkenyl group induced from olefin oligomer such as propylene, 1-butene, isobutylene, or co-oligomer of ethylene and propylene.

In the invention, when ashless dispersant other than modified alkyl or alkenyl borate succinimde is mixed, the content thereof is not particularly limited, for total amount of the composition, normally it is from 0.1˜20% by mass, preferably 3˜15% by mass.

Examples of friction modifier include ashless friction modifier such as amine compound, fatty acid ester, fatty acid amide, fatty acid, alphatic alcohol, aliphatic ether, hydrazide (oleylhydrazide, and the like), semicarbazide, urea, ureido, biuret, respectively having at least an alkyl groups or an alkenyl groups of carbon number 6 to 30, particularly a straight-chain type alkyl groups or a straight-chain type alkenyl groups of carbon number 6 to 30 in the molecule. The friction modifier can be normally added in the range of 0.15% by mass.

Examples of viscosity index improver particularly include: the so-called “non-dispersed viscosity index improver” such as polymer or copolymer made of one or more kinds of monomer selected from the various types of methacrylic acid ester, or hydrogenated compound thereof; or the so-called “dispersion-type viscosity index improver” obtained by the copolymerization of various types of methacrylic acid ester containing nitrogen compounds; nondispersed or dispersed ethylene-a-olefin copolymer (as α-olefin, propylene, 1-butene, 1-pentene can be shown.) or hydrogenated compound thereof; polyisobutylene or hydrogenated compound thereof; hydrogenated styrene-dien copolymer; styrene-maleic anhydride ester copolymer and polyalkylstyrene.

Molecular weight of such viscosity index improver needs to be determined in consideration of shear stability. In particularly, examples of number average molecular weight of the viscosity index improver is as follows: in case of dispersed or non-dispersed type polymethacrylate, it is normally in the range of 5,000˜1,000,000, preferably 100,000˜900,000; in case of polyisobutylene or hydrogenated compound thereof, it is normally in the range of 800˜5,000, preferably 1,000˜4,000; in case of ethylene-α-olefin copolymer or hydrogenated compound thereof, it is normally in the range of 800˜500,000, preferably 3,000˜200,000.

Among the above viscosity index improvers, when ethylene-α-olefin copolymer or hydrogenated compound thereof is used, a lubricant composition which is particularly excellent in shear stability can be obtained. One or more kinds of compounds selected from the above viscosity index improvers can be added, if necessary. Content of the viscosity index improvers is, for total amount of lubricant composition, 0.1˜20% by mass.

As corrosion inhibitor, the examples are compounds of benzotriazole series, tolyltriazole series, thiadiazole series, and imidazole series.

As rust inhibitor, examples include petroleum sulfonate, alkylbenzene sulfonate, dinonylnaphthalene sulfonate, alkenyl succinic acid ester, polyvalent alcohol ester, and so on.

As anti-emulsifying agent, examples include polyalkylene glycol series nonionic surfactant such as polyoxyethylene alkylether, polyoxyethylene alkylphenylether, and polyoxyethylene alkylnaphthylether.

As metal deactivator, the examples include imidazoline, pyrimidine derivatives, alkylthiadiazole, mercaptobenzothiazole, benzotriazole or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bisdialkyldithiocarbamate, 2- (alkyldithio) benzoimidazole, and p- (o-carboxy benzylthio) propionnitrile.

As defoamant, the examples include silicone, fluorosilicol, and fluoroalkylether.

When these additives are added in the lubricant composition of the invention, for total amount of the composition: the content of corrosion inhibitor, rust inhibitor, and anti-emulsifying agent, respectively, are normally selected in the range of 0.005˜5% by mass; the content of metal deactivator is normally selected in the range of 0.005˜1% by mass; and the content of defoamant is selected in the range of 0.0005˜1% by mass.

The lubricant composition of the invention is a composition which can inhibit corrosion or corrosive-wear of metallic materials containing lead even though the content of zinc dithiophosphate as phosphorus amount is 0.08% by mass or less. If necessary, it is possible to make low-sulfur lubricant composition whose total sulfur content is 0.3% by mass or less. Depending on the selection of lubricant base oil or various additives, it is also possible to obtain the lubricants whose total sulfur content is 0.2% by mass or less, more preferably 0.1% by mass or less, particularly preferably 0.05% by mass or less or 0.01% by mass or less, and substantially 0% by mass.

Moreover, the lubricant composition of the invention is a composition whose content of sulfated ash can be set to 1.0% by mass or less by adjusting the content of the additives. Also, in order to inhibit the ash to accumulate in exhaust gas aftertreatment apparatus and combustion chamber, the content is desirable to set the range such as preferably 0.8% by mass, more preferably 0.6% by mass or less, particularly 0.5% by mass or less.

The lubricant composition is low-sulfur, excellent in anticorrosive and anticorrosive-wear property of metallic materials containing lead, low-friction property, long drain performance (oxidation stability, base number preservation, etc.), and high-temperature detergency. Thus it can be preferably used as lubricant for internal combustion engine. Also, to make it low-sulfur, low-phosphorus, low-ash lubricant, the lubricant composition becomes particularly suitable for use in internal combustion engine where exhaust-gas aftertreatment apparatus is attached. Further, it is suitable for lubricant for internal combustion engine using low-sulfur fuels such as fuel whose sulfur portion is 50 ppm by mass or less, more preferably 30 ppm by mass or less, particularly preferably 10 ppm by mass or less (e.g., gasoline, gas oil, kerosene, alcohol, dimethylether, LPG, natural gas, etc.). Especially, it can be suitably used as a lubricant for diesel engines or gas engines having sliding materials containing lead, among them, it is particularly preferably used as lubricant for gas engines.

In addition, the lubricant composition of the invention having contact with metallic materials containing lead can be suitably used for lubricant for drive-train such as automatic or manual transmission; grease, wet-type brake oil, hydraulic oil, turbine oil, compressor oil, bearing oil, lubricant for refrigerant oil and the like.

EXAMPLES

Hereinafter, the invention will be more specifically described by way of the following examples and comparative examples. However, it is not limited by such examples.

Examples 1˜12, Comparative Examples 1˜3

The lubricant compositions of the invention (examples 1˜12) and lubricant composition for the comparison (comparative examples 13) were respectively prepared based on Table 1.

(Table 1) TABLE 1 Example Example Example Example Example Example Example Example 1 2 3 4 5 6 7 8 Lubricant base oil ※1) % by mass remnant remnant remnant remnant remnant remnant remnant remnant Lubricant base oil ※2) % by mass — — — — — — — — MoDTP ※3) % by mass — — — — — — — — MoDTC ※4) % by mass — — — — — — — — Mo salt of carboxylic acid ※5) % by mass — — — — — — — — Mo amine complex ※6) % by mass 0.05 0.1 0.3 0.7 — — — — Mo phosphate ※7) % by mass — — — — 0.2 — — 0.5 Mo ester ※8) % by mass — — — — — 1.7 — — Alkanolamide Mo ester ※9) % by mass — — — — — — 1.7 — Molybdenum content % by mass (0.005) (0.01) (0.03) (0.07) (0.013) (0.02) (0.02) (0.033) Zinc dithiophosphate ※10) % by mass — — — — — — — — Phosphorus content % by mass — — — — — — — — Metallic detergent ※11) % by mass 3 3 3 3 3 3 3 3 Metal content % by mass (0.18) (0.18) (0.18) (0.18) (0.18) (0.18) (0.18) (0.18) Ashless dispersant ※12) % by mass 5 5 5 5 5 5 5 5 Antioxidant ※13) % by mass 2 2 2 2 2 2 2 2 Pb content after NOx in 48 hours 340 340 330 340 340 360 350 360 absorbing test (140° C.) in 72 hours 1100 1200 1100 1200 1200 1200 1200 1200 (ppm by mass) Cu content after ISOT in 96 hours 7 8 5 8 4 6 8 3 (165.5° C.) (ppm by mass) Example Example Comparative Comparative Example Example Comparative 9 10 Example 1 Example 2 11 12 Example 3 Lubricant base oil ※1) % by mass — — remnant remnant remnant remnant remnant Lubricant base oil ※2) % by mass remnant remnant — — — — — MoDTP ※3) % by mass — — — 0.2 — — — MoDTC ※4) % by mass — — — — 0.4 — — Mo salt of carboxylic acid ※5) % by mass — — — — — 0.15 — Mo amine complex ※6) % by mass 0.2 0.5 — — — — — Mo phosphate ※7) % by mass — — — — — — — Mo ester ※8) % by mass — — — — — — — Alkanolamide Mo ester ※9) % by mass — — — — — — — Molybdenum content % by mass (0.02) (0.05) (0.00) (0.018) (0.018) (0.023) (0.00) Zinc dithiophosphate ※10) % by mass — — — — — — 1.05 Phosphorus content % by mass — — — — — — (0.08) Metallic detergent ※11) % by mass 3 3 3 3 3 3 3 Metal content % by mass (0.18) (0.18) (0.18) (0.18) (0.18) (0.18) (0.18) Ashless dispersant ※12) % by mass 5 5 5 5 5 5 5 Antioxidant ※13) % by mass 2 2 2 2 2 2 2 Pb content after NOx in 48 hours 340 150 520 650 340 450 320 absorbing test (140° C.) (ppm by mass) in 72 hours 1200 1200 3600 4800 1500 2400 1300 Cu content after ISOT in 96 hours 12 15 5 50 40 5 95 (165.5° C.) (ppm by mass) ※1) Hydrocracked base oil, Kinematic viscosity at 100 C.: 5.3 mm²/s, viscosity index: 123, sulfur content: less than 0.001% by mass. ※2) Solvent refined base oil, Kinematic viscosity at 100° C.: 5.7 mm²/s, viscosity index: 100, sulfur content: 0.1% by mass. ※3) Molybdenum-2-ethylhexyl dithiophosphate, Mo content: 9.0% by mass, sulfur content: 10.5% by mass, phosphorus content: 9.0% by mass. ※4) Molybdenum-2-ethylhexyl dithiocarbamate, Mo content: 4.5% by mass, sulfur content: 5.0% by mass. ※5) Molybdenum 2-ethylhexyl acid, Mo content: 15% by mass, sulfur content: 0% by mass. ※6) Molybdenum ditridecylamine complex, Mo content: 9.7% by mass, sulfur content: 0% by mass. ※7) Molybdenum phosphate, alkyl group is 2-ethylhexyl group, Mo content: 6.5% by mass, phosphorus content: 4.6% by mass, .sulfur content: 0% by mass. ※8) Molybdenum ester of glycerin monooleate, Mo content: 1.2% by mass, sulfur content: 0% by mass. ※9) Molybdenum ester of oleic acid diethanolamide, Mo content: 1.2% by mass, sulfur content: 0% by mass. ※10) Alkyl group: sec-butyl/hexyl group, phosphorus content: 7.2% by mass, sulfur content: 15.2% by mass, zinc content: 7.8% by mass. ※11) Calcium salicylate, total base number: 170 mgKOH/g, calcium content: 6.1% by mass, metal ratio: 2.8. ※12) Polybutenyl succinimide, number average molecular weight of polybutenyl group: 1300, nitrogen content: 1.8% by mass, boron content: 0.77% by mass. ※13) Phenolic and amine Antioxidant (1:1).

To the obtained individual composition, the following evaluation tests were carried out.

(Variation with Time of Amount of Lead Elution by NOx Absorbing Test)

To testing oil which received a copper piece under the condition based on the drafts of Japan Tribology Conference 1992, 10, 465 (i.e., 140° C., NOx: 1185 ppm), NOx gas was blown, then variation with time of amount of lead elution under compulsory deterioration was measured. If the amount of lead elution is small, it means that the testing oil can inhibit the corrosion of lead. By having NOx absorbing test under compulsory deterioration, it is possible to check oil deterioration, especially to check the impact of deterioration product generated by the deterioration of lubricant for internal combustion engine on metal corrosion in a short time.

(Variation with Time of Amount of Lead Elution by ISOT)

With use of testing oil which received a copper test piece under the condition based on JIS-K2514 (i.e., 165.5° C.), amount of copper elution was measured in 96 hours. If the amount of copper elution is small, it means that the testing oil can inhibit the corrosion of copper.

(Evaluation Result)

As clearly seen from Table 1, the composition of comparative example 1 without containing organomolybdenum compound and a composition of the compatarive example 2 containing molybdenum compound which is not specified by the present invention, overall, had extremely large amount of lead elution. The comparative example 3 to which 0.08% by mass of zinc dithiophosphate was added as the phosphorus amount, to the contrary, although lead elution was inhibited, amount of copper elution was extremely large. From these results, it is understood that conventional corrosion inhibitors have difficulties to inhibit elution of lead and copper at the same time.

On the other hand, compositions of the examples 1˜12 containing molybdenum compounds of the invention had results that the amount of both lead and copper elution were low compared with the comparative examples. From this fact, it can be seen that the composition containing molybdenum compounds of the invention can inhibit corrosion of copper and lead.

Examples 13˜21, Comparative Example 4

The lubricant compositions of the invention (examples 13˜21) and lubricant composition for the comparison (comparative example 4) were respectively prepared based on Table 2.

(Table 2) TABLE 2 Example Example Example Example Example Example 13 14 15 16 17 18 Lubricant base oil ※1) % by mass remnant remnant remnant remnant remnant remnant Tri-n-butylborate ※2) % by mass 0.3 — 0.3 — 0.3 — Tri-2-ethylhexylborate ※3) % by mass — 0.5 — 0.5 — 0.5 Boron content % by mass (0.015) (0.015) (0.015) (0.015) (0.015) (0.015) Mo amine complex ※4) % by mass — — 0.1 0.1 0.5 0.5 Molybdenum content % by mass — — (0.01) (0.01) (0.05) (0.5) Salicylate A ※5) % by mass 2 2 2 2 2 2 Salicylate B ※6) 1 1 1 1 1 1 Metal content % by mass (0.23) (0.23) (0.23) (0.23) (0.23) (0.23) Ashless dispersant ※7) % by mass 5 5 5 5 5 5 Antioxidant ※8) % by mass 1 1 1 1 1 1 Pb content after NOx absorbing in 48 hours 340 340 340 350 340 350 test (140° C.) (ppm by mass) in 70 hours 2400 2300 1200 1200 1100 1200 Example Example Comparative Example 19 20 Example 4 21 Lubricant base oil ※1) % by mass remnant remnant remnant remnant Tri-n-butylborate ※2) % by mass 1.5 — — — Tri-2-ethylhexylborate ※3) % by mass — 1.5 — — Boron content % by mass (0.075) (0.075) — — Mo amine complex ※4) % by mass 0.1 0.1 — 0.1 Molybdenum content % by mass (0.01) (0.01) — (0.01) Salicylate A ※5) % by mass 2 2 2 2 Salicylate B ※6) 1 1 1 1 Metal content % by mass (0.23) (0.23) (0.23) (0.23) Ashless dispersant ※7) % by mass 5 5 5 5 Antioxidant ※8) % by mass 1 1 1 1 Pb content after NOx absorbing in 48 hours 320 310 1900 1700 test (140° C.) (ppm by mass) in 70 hours 1100 1100 4200 3500 ※1) Hydrocracked base oil, Kinematic viscosity at 100° C.: 5.3 mm²/s, viscosity index: 123. ※2) Boron content: 4.8% by mass. ※3) Boron content: 2.8% by mass. ※4) Molybdenum ditridecylamine complex, Mo content: 9.7% by mass, sulfur content: 0% by mass. ※5) Monoalkyl type, alkyl group: sec-C14-C18, base number: 170 mgKOH/g, metal ratio: 2.8, calcium content: 6.1% by mass. ※6) Monoalkyl type, alkyl group: sec-C14-C18, base number: 280 mgKOH/g, metal ratio: 5.5, calcium content: 10% by mass. ※7) Polybutenyl succinimide, number average molecular weight of polybutenyl group: 1300, nitrogen content: 1.8% by mass. ※8) Phenolic and amine Antioxidant (1:1).

To the obtained individual compositions, the following evaluation tests were carried out.

(Variation with Time of Amount of Lead Elution by NOx Absorbing Test)

The variation with time of amount of lead elution by NOx absorbing test was measured in the same manner as that of Table 1.

(Evaluation Result)

The composition of comparative example 4 in Table 2 was the composition which did not contain both borate ester and organomolybdenum compounds, it had extremely large amount of lead elution at 140° C.

The composition of examples 13 and 14 in Table 2 were the composition containing borate ester; the composition of examples 15˜20 were the composition containing both borate ester and organomolybdenum compounds; the composition of example 21 was the composition containing organomolybdenum compounds. In these examples, compared with the comparative example, the lead elution was inhibited. Especially, the lead elution of examples 15˜20 containing both borate ester and organomolybdenum compounds in 70 hours were remarkably inhibited.

Examples 22˜29, Comparative Example 5

The lubricant compositions of the invention (examples 22˜29) and lubricant composition for the comparison (comparative example 5) were respectively prepared based on Table 3.

(Table 3) TABLE 3 Example Example Example Example Example 22 23 24 25 26 Lubricant base oil ※1) % by mass remnant remnant remnant remnant remnant Mo amine complex ※2) % by mass 0.05 0.1 0.2 0.5 0.7 Molybdenum content % by mass (0.005) (0.01) (0.02) (0.05) (0.07) Borated succinimide ※3) % by mass 5 5 5 5 5 Succinimide ※4) % by mass — — — — — Boron content % by mass (0.035) (0.035) (0.035) (0.035) (0.035) Phosphorus compound ※5) 0.53 0.53 0.53 0.53 0.53 Phosphorus content (0.07) (0.07) (0.07) (0.07) (0.07) Salicylate ※6) % by mass 3 3 3 3 3 Metal content % by mass (0.18) (0.18) (0.18) (0.18) (0.18) Antioxidant ※7) % by mass 1 1 1 1 1 Pb content after NOx absorbing in 48 hours 340 340 340 350 340 test (140° C.) (ppm by mass) in 70 hours 1800 1400 1200 1200 1100 Example Example Comparative Example 27 28 Example 5 29 Lubricant base oil ※1) % by mass remnant remnant remnant remnant Mo amine complex ※2) % by mass 0.2 0.2 — 0.2 Molybdenum content % by mass (0.02) (0.02) — (0.02) Borated succinimide ※3) % by mass 2.5 10 5 — Succinimide ※4) % by mass — — — 5 Boron content % by mass (0.017) (0.077) (0.035) — Phosphorus compound ※5) 0.53 0.53 0.53 0.53 Phosphorus content (0.07) (0.07) (0.07) (0.07) Salicylate ※6) % by mass 3 3 3 3 Metal content % by mass (0.18) (0.18) (0.18) (0.18) Antioxidant ※7) % by mass 1 1 1 1 Pb content after NOx absorbing in 48 hours 350 320 520 910 test (140° C.) (ppm by mass) in 70 hours 1200 1100 4200 2400 ※1) Hydrocracked base oil, Kinematic viscosity at 100° C.: 5.3 mm²/s, viscosity index: 123, sulfur portion: less than 0.001% by mass. ※2) Molybdenum ditridecylamine complex, Mo content: 9.7% by mass, sulfur content: 0% by mass. ※3) Number average molecular weight of polybutenyl group: 1300, nitrogen content: 1.8% by mass, boron content: 0.77% by mass. ※4) Polybutenyl succinimide, number average molecular weight of polybutenyl group: 1300, nitrogen content: 1.8% by mass. ※5) Zinc di-n-butylphosphate, phosphorus content: 13.2% by mass, sulfur content: 0% by mass, zinc content: 13% by mass. ※6) Base number: 170 mgKOH/g, metal ratio: 2.8, calcium content: 6.1% by mass. ※7) Phenolic and amine Antioxidant (1:1).

To the obtained individual compositions, the following evaluation test were carried out.

(Variation with Time of Amount of Lead Elution NOx Absorbing Test)

The variation with time of amount of lead elution by NOx absorbing test was measured in the same manner as that of Table 1.

(Evaluation Result)

The composition of comparative example 5 in Table 3 was the composition only containing modified alkyl borate. Lead elution thereof at 140° C. was 520 ppm by mass in 48 hours and 4200 ppm by mass in 70 hours; the amount in each times were extremely large.

The compositions of examples 22˜28 in Table 3 were the compositions containing both organomolybdenum compounds and modified alkenyl borate succinimide. In these examples, compared with the comparative examples, the lead elution both in 48 hours and 70 hour were inhibited. Moreover, example 29 was a composition containing organomolybdenum compounds, compared with the comparative example, the lead elution in 70 hours was inhibited. 

1. A lubricant composition comprising a lubricant base oil, wherein said lubricant composition contains 0.08% by mass or less of zinc dithiophosphate or no zinc dithiophosphate as phosphorus amount for total amount of said lubricant composition, contacts metallic materials containing lead, and contains at least a kind of additive selected from a group consisting of following (A)˜(D): (A) organomolybdenum compounds (except molybdenum dithiophosphate); (B) borate ester and/or derivatives thereof; (C) organomolybdenum compounds, and borate ester and/or derivatives thereof; and (D) organomolybdenum compounds, and borated alkyl or alkenyl succinimide.
 2. A lubricant composition according to claim 1, wherein said organomolybdenum compounds are compounds obtained by reaction of any one kind of compound selected from a group consisting of: sulfur-free organic acid, amine, amide, imide, and compounds having alcoholic hydroxyl group, with tetra- to hexa-valent molybdenum compounds.
 3. A lubricant composition according to claim 1, wherein said organomolybdenum compounds are at least any one kind of compound selected from a group consisting of following (a)˜(e): (a) a salt of at least a kind of acid containing phosphorus selected from a group consisting of: phosphite monoester, phosphate monoester, phosphite diester, phosphate diester, phosphonous acid, phosphonic acid, phosphonous acid monoester, and phosphonic acid monoester, respectively having at least an alkyl group of carbon number 3 to 30, with molybdenum compounds; (b) a complex of a kind of amine compound selected from a group consisting of: primary amine, secondary amine, and alkanolamine, respectively having at least an alkyl group or an alkenyl group of carbon number 3 to 30, with molybdenum compounds; (c) a salt or an ester of alcohols having at least an alcoholic hydroxyl group selected from a group consisting of: monovalent alcoholes, polyvalent alcohols, and partial ester or partial ether of the polyvalent alcohols of carbon number 3 to 30, with molybdenum compounds; (d) a salt or an ester of amide compounds having at least an alkyl group or an alkenyl group of carbon number 3 to 30 and alcoholic hydroxyl groups, with molybdenum compounds; and (e) a salt of fatty acids of carbon number 3 to 30 with molybdenum compounds.
 4. A lubricant composition according to claim 1, further comprising one or more kind of additives selected from a group consisting of: antioxidant, anti-wear agent other than zinc dithiophosphate, and metallic detergent.
 5. A lubricant composition according to claim 1, wherein said lubricant composition is used for internal combustion engine of which slide members contain a metallic materials containing lead.
 6. A lubricant composition according to claim 1, wherein said lubricant composition contacts metallic materials containing lead, metallic materials containing copper-lead, or both of the metallic materials containing lead and the metallic materials containing copper, and wherein said organomolybdenum compounds are compounds obtained by reaction of any one kind of compound selected from a group consisting of: sulfur-free organic acid except carboxylic acid, amine, amide, imide, and compounds having alcoholic hydroxyl groups, with tetra- to hexa-valent molybdenum compounds.
 7. A method for inhibiting corrosion or corrosive wear of a metallic materials containing lead having a contact with a lubricant composition comprising a lubricant base oil, wherein said lubricant composition contains 0.08% by mass or less of zinc dithiophosphate or no zinc dithiophosphate as phosphorus amount for total amount of said lubricant composition, and said lubricant composition contains at least a kind of additive selected from a group consisting of following (A)˜(D): (A) organomolybdenum compounds (except molybdenum dithiophosphate); (B) borate ester and/or derivatives thereof; (C) organomolybdenum compounds, and borate ester and/or derivatives thereof; and (D) organomolybdenum compounds, and borated alkyl or alkenyl succinimide.
 8. A method for inhibiting corrosion or corrosive wear according to claim 7, wherein said method inhibits corrosion or corrosive wear of metallic materials containing lead, metallic materials containing copper-lead, or both of the metallic materials containing lead and the metallic materials containing copper, and wherein organomolybdenum compounds among said additives are compounds obtained by reaction of any one kind of compound selected from a group consisting of: sulfur-free organic acid except carboxylic acid, amine, amide, imide, and compounds having alcoholic hydroxyl groups, with tetra- to hexa-valent molybdenum compounds.
 9. An anticorrosion or anticorrosive-wear agent for copper and lead, wherein said agent is an additive added to a lubricant composition comprising a lubricant base oil, contains 0.08% by mass or less of zinc dithiophosphate or no zinc dithiophosphate as phosphorus amount for total amount of said lubricant composition, contacts metallic materials containing lead, metallic materials containing copper-lead, or both of the metallic materials containing lead and the metallic materials containing copper, and further contains organomolybdenum compounds obtained by reaction of any one kind of compound selected from a group consisting of: sulfur-free organic acid except carboxylic acid, amine, amide, imide, and compounds having alcoholic hydroxyl group, with tetra- to hexa-valent molybdenum compounds.
 10. A use of a lubricant composition for lubricating metallic materials containing lead in a machine having metallic materials containing lead therein, wherein said lubricant composition comprises a lubricant base oil, contains 0.08% by mass or less of zinc dithiophosphate or no zinc dithiophosphate as phosphorus amount for total amount of said lubricant composition, and contains at least a kind of additive selected from a group consisting of following (A)˜(D) (A) organomolybdenum compounds (except molybdenum dithiophosphate); (B) borate ester and/or derivatives thereof; (C) organomolybdenum compounds, and borate ester and/or derivatives thereof; and (D) organomolybdenum compounds, and borated alkyl or alkenyl succinimide. 